This is the name of the motu proprio which establishes the liberalization of the Traditional form of the Roman Rite and rules for its implementation, according to I.MEDIA, which has confirmed that it will be published on July 7, 2007.
UPDATE (1600 GMT): M. Antoine-Marie Izoard, director of I.MEDIA, has courteously granted us the possibility to make public the following excerpts of this morning's exclusive dispatch (Copyright I.MEDIA):
Vatican - Agency I.MEDIA - July 4 2007
The Motu Proprio "Summorum Pontificum" for the liberalization of the Mass according to the Missal of 1962 will be published on July 7
The Apostolic Letter in the form of Motu Proprio which Benedict readies to publish in order to liberalize the use of the Mass and liturgical books according to the pre-Conciliar rite of 1962 will receive the name of "Summorum Pontificum", I.MEDIA has learned from Vatican sources. This document, greatly expected by the Traditionalist faithful and feared by a certain number of Bishops, will be published on July 7.
Summorum Pontificum (in [English], "...of the Supreme Pontiffs") is the incipit (beginning of the text) of the Motu Proprio of Benedict XVI liberalizing the use of the Mass said of "Saint Pius V", I.MEDIA has learned from Vatican sources. This Apostolic Letter which will be made public next July 7. The document will be accompanied by a long letter by the Pope explaining his motivations for this publication of which certain Bishops, particularly in France, disapprove [lit. "take a dim view"].
As for other news on the contents of the document, we will remind our readers of our caveat:
Considering the closeness of the date of publication of the motu proprio on the liberalization of the Traditional Roman Rite and its accompanying letter, we will avoid commenting on the contents of both documents, until the actual texts are publicly known.
With 60 hours left until the official release of the document, every speculation on the contents of Summorum pontificum would be inappropriate. For those who may be curious, we direct them to this Apic article in French, which includes much of the I.Media material and other details which are, for the most part, well known to those who have been following the debate.