Here is the Vatican-provided text from the Congregation for the Doctrine of the Faith, published today, March 25, 2020.
Note for the presentation of the Decree Quo magis
approving seven Eucharistic Prefaces
for the forma extraordinaria of the Roman Rite
With the Decree Quo magis of 22 February 2020, the Congregation for the Doctrine of the Faith, which since January 2019 deals with those matters formerly assigned to the Pontifical Commission “Ecclesia Dei”, has approved the text of seven new Eucharistic Prefaces to be used ad libitum in the celebration of Mass according to the forma extraordinaria of the Roman Rite.
This Decree constitutes the completion of the work previously initiated by the aforementioned Pontifical Commission in order to carry out the mandate given by Pope Benedict XVI to add some additional Prefaces to the Missal of the forma extraordinaria.
The studies carried out lead to the selection of a limited number of texts, to be used for particular occasions such as feasts of Saints, votive Masses or ad hoc celebrations, without making any changes to the celebration of the temporal cycle. This choice was made in order to safeguard, through the unity of texts, the unanimity of sentiments and of prayer that are appropriate for the confession of the mysteries of Salvation celebrated in what constitutes the backbone of the liturgical year. In addition, the historical development of the Corpus Præfationum of the Missale Romanum up until the middle of the 20th Century shows a general movement towards the use of new prefaces for occasional celebrations rather than for celebrations of the temporal cycle.
At the same time, the opportunity was taken to extend to all those who celebrate in the Usus Antiquior the faculty to use three other Prefaces previously approved for certain places. These too are texts for determined occasional celebrations.
Four of the newly approved texts, namely the Prefaces de Angelis, de Sancto Ioanne Baptista, de Martyribus and de Nuptiis, are taken from the Missal of the forma ordinaria, and for the most part their central section, known as the “embolism”, appear in ancient liturgical sources. In order to guarantee consistency with the rest of the Corpus Præfationum of the old Missal, in three cases, the standard forms of Preface conclusion of the forma extraordinaria have been used. As indicated, the three other texts (Prefaces de Omnibus Sanctis et Sanctis Patronis, de Sanctissimo Sacramento and de Dedicatione ecclesiæ) are Prefaces previously granted to French and Belgian Dioceses, where they were in use before the post-conciliar liturgical reform. From now on, these may be used wherever Mass is celebrated in the forma extraordinaria.
Two of the seven Prefaces will allow to aptly give more prominence to liturgical celebrations in honour of certain leading figures in God’s design, as manifested in the history of Salvation, namely the Angels and St. John the Baptist, which hitherto both lacked a proper Eucharistic Preface in the Usus Antiquior. In the same vein, the Preface de Martyribus will allow to further underline the eminent character of the gift of martyrdom among the other witnesses of Sequela Christi. Indeed, the first Saints recognized as such were the Martyrs. The Prefaces de Dedicatione Ecclesiæ, de Omnibus Sanctis et Sanctis Patronis and de Ss.mo Sacramento, already in use in some places, will appropriately enrich the celebrations in question with a more suitable eucology than the standard Præfatio Communis. Finally, special note should be taken of the Preface de Nuptiis, which together with the long Nuptial Blessing still in use in Masses pro Sponsis, is to be found – with minor variations – in early Sacramentaries such as the Gelasianum Vetus or the Gregorianum. This ancient Preface, already existing in the forma ordinaria, may therefore now be used in the forma extraordinaria as well.
As indicated above, the use or not, in the relevant circumstances, of the newly approved Prefaces remains an ad libitum choice. Obviously, the celebrant is expected to make use of good pastoral common sense in this regard. In addition, it should be noted that the Decree does not cancel any eventual concessions of proper Prefaces granted in the past, and therefore in those particular cases where there already exists, on the basis of preceding permissions, and for the same liturgical circumstance, a different particular Preface, one may choose between that Preface and the newly approved text.
______________________ Cf. Francis, Apostolic Letter in the form of Motu Proprio on the Pontifical Commission “Ecclesia Dei”, 17 January 2019.  The texts of these Prefaces, with the musical notation according to the various tones in use in the forma extraordinaria, will be available at the Libreria Editrice Vaticana.  “Some of the new Prefaces can and should be inserted in the old Missal. The “Ecclesia Dei” Commission, in contact with various bodies devoted to the Usus Antiquior, will study the practical possibilities in this regard”: Benedict XVI, Letter to the Bishops on the occasion of the publication of the Apostolic Letter “Motu Proprio Data” Summorum Pontificum on the use of the Roman Liturgy prior to the reform of 1970, AAS 99 (2007) 798. This mandate was further confirmed and completed in 2011 by the Instruction Universæ Ecclesiæ of the same Pontifical Commission: cf. Pontifical Commission “Ecclesia Dei”, Instruction on the Application of the Apostolic Letter Summorum Pontificum of His Holiness Benedict XVI given Motu Proprio, no. 25, AAS 103 (2011) 418.
CONGREGATIO PRO DOCTRINA FIDEI
Quo magis altera Ritus Romani forma alteram locupletaret, in Epistula ad universos Ecclesiæ latinæ Episcopos die VII mensis Iulii a. D. MMVII data, censuit Benedictus PP. XVI aliquot ex novis præfationibus veteri Missali esse inserendas.
Cum enim Pontificia Commissio “Ecclesia Dei” eam sententiam per instructionem Universæ Ecclesiæ confirmavisset, eadem Commissio, de mandato eiusdem Benedicti XVI in dicta epistula dato et a fontibus novis veteribusque hauriens, investigationem de aptioribus rationibus præfationum in antiquo Missali adiungendarum aggressa est. Eam vero investigationem ab illa Pontificia Commissione inchoatam Congregatio pro Doctrina Fidei modo absolvit, postquam Litteris Apostolicis die XVII mensis Ianuarii a. D. MMXIX motu proprio datis Summus Pontifex Franciscus omnia munera supra dictæ Commissionis in illam Congregationem transtulit.
Quapropter Congregatio pro Doctrina Fidei, consultis nonnullis institutis religiosis, societatibus vitæ apostolicæ, et viris peritis usui antiquiori illigatis, necnon Em.mo Card. Præfecto Congregationis de Cultu Divino et Disciplina Sacramentorum, septem præfationes, uti in adiecto inveniuntur exemplari, probat, et concedit ut a quolibet sacerdote Sacrificium Eucharisticum ad normas Litterarum Apostolicarum Summorum Pontificum secundum Missale Romanum anni MCMLXII celebrante, servatis rubricis appositis, adhiberi possint.
Quæcumque hoc Decreto statuta sunt, a die XIX mensis Martii huius anni, in festo S. Ioseph, Sponsi Beatæ Mariæ Virginis, Confessoris et Ecclesiæ Universæ Patroni, serventur, contrariis quibuscumque minime obstantibus.
Summus Pontifex Franciscus, in Audientia die V mensis Decembris a. D. MMXIX infrascripto Archiepiscopo Secretario Congregationis pro Doctrina Fidei concessa, hoc Decretum ratum habuit et publici iuris fieri iussit.
Datum Romæ, ex Ædibus Congregationis pro Doctrina Fidei, die XXII mensis Februarii a.D. MMXX, in festo Cathedræ S. Petri Apostoli.
Aloisius F. Card. Ladaria, S.I.
Congregationis pro Doctrina Fidei Præfectus
X Iacobus Morandi
Archiepiscopus tit. Cæretanus
______________________ Benedictus XVI, Epistula ad Episcopos ad producendas Litteras Apostolicas Motu Proprio datas, de Usu Liturgiæ Romanæ Instaurationi anni 1970 præcedentis, AAS 99 (2007), 798.  Pontificia Commissio “Ecclesia Dei”, Instructio ad exsequendas Litteras Apostolicas Summorum Pontificum a S. S. Benedicto PP. XVI Motu Proprio datas, AAS 103 (2011), 413-420, n. 25.  Franciscus, Litteræ Apostolicæ Motu Proprio datæ de Pontificia Commissione “Ecclesia Dei”, die 17 Ianuarii 2019.