First of all a bit more mischief tucked away in Universae Ecclesiae. The first of the aims of the provisions of Summorum Pontificum cited in n.8 of the Instruction is:
a.) offering to all the faithful the Roman Liturgy in the Usus Antiquior, considered as a precious treasure to be preservedA "parallel passage" to this cannot be found in Summorum Pontificum. It is true that the provisions of Summorum Pontificum intend that all the faithful who wish it can participate more easily in celebrations in the extraordinary form (and, of course, we should read the Instruction about implementing the Motu Proprio in the light of the Motu Proprio itself and not in isolation from it). The preamble and article 1 of Summorum Pontificum make this clear:
But in some regions, no small numbers of faithful adhered and continue to adhere with great love and affection to the earlier liturgical forms. These had so deeply marked their culture and their spirit that in 1984 the Supreme Pontiff John Paul II, moved by a concern for the pastoral care of these faithful, with the special indult "Quattuor Abhinc Anno," issued by the Congregation for Divine Worship, granted permission to use the Roman Missal published by Blessed John XXIII in the year 1962. Later, in the year 1988, John Paul II with the apostolic letter given as "motu proprio, "Ecclesia Dei," exhorted bishops to make generous use of this power in favor of all the faithful who so desired.We also need to bear in mind the agenda of "mutual enrichment" referred to by Pope Benedict in his letter that accompanied Summorum Pontificum:
Following the insistent prayers of these faithful, long deliberated upon by our predecessor John Paul II, and after having listened to the views of the cardinal fathers of the consistory of 22 March 2006, having reflected deeply upon all aspects of the question, invoked the Holy Spirit and trusting in the help of God, with these apostolic letters we establish the following:
Art 1. .... It is, therefore, permissible to celebrate the Sacrifice of the Mass following the typical edition of the Roman Missal promulgated by Blessed John XXIII in 1962 and never abrogated, as an extraordinary form of the liturgy of the Church.
For that matter, the two Forms of the usage of the Roman Rite can be mutually enriching: new Saints and 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. The celebration of the Mass according to the Missal of Paul VI will be able to demonstrate, more powerfully than has been the case hitherto, the sacrality which attracts many people to the former usage.I think there are three things to be said about the provision of n.8 (a) of Universae Ecclesiae. If it is read in the context of Summorum Pontificum, it does not mean, as some might wish, that the extraordinary form should be celebrated in every parish every Sunday. It does mean that those who have an attachment to the extraordinary form should have a kind of "natural right" to participate in celebrations of that form rather than needing a "special permission", and that appropriate logistics are in place to enable this. The phrase "all the faithful" should be read, when responding to this question about the frequency of celebrations, with reference to those who are attached to the extraordinary form.
However, I do think the more ready celebration of the extraordinary form is offered to "all the faithful" - by which I mean now those who do not have an attachment to the extraordinary form. This offer is mediated through the idea of "mutual enrichment". Once it is recognised that there is no contradiction between the ordinary and extraordinary forms, then it should be possible to see in the ordinary form those elements of the "precious treasure" that come to greater visibility because of their now being seen in a relation to the extraordinary form.
One of the least commented upon points of Universae Ecclesiae is n.25:
25. New saints and certain of the new prefaces can and ought to be inserted into the 1962 Missal, according to provisions which will be indicated subsequently.There is clear indication here that the Pontifical Commission "Ecclesia Dei" are working on the "mutual enrichment" from the aspect of its significance for the celebration of the extraordinary form. What I would hope is that, as they undertake the two specific tasks referred to in n.25, they will also look at the question of unifying the calendars of the two forms. This would make it much easier for those who look to enrich the celebration of the ordinary form from that of the extraordinary form, as well as better serving the intention of unity in the Church that is another of the intentions of Summorum Pontificum.
However, perhaps the underlying difficulty is that the Commission "Ecclesia Dei" do not appear to have the (mutual) enrichment of the ordinary form within their brief, though Summorum Pontificum suggested that they had an overview of its provisions that might have included this. There seems to be no clear allocation of this responsibility within the dicasteries of the Holy See. It could, of course, be undertaken at the level of the local Church. Unless it is undertaken, a key aspect of the "offering to all the faithful" of the extraordinary form will not be achieved.