The Italian press is not always the best source of accurate news. Rumors, yes. Still, when you get enough suggestions of a story, something can be said to be brewing.
I saw a copy of Corriere della Sera, which is sort of the NYT of Italy. Their vaticanista, Luigi Accattoli (pronounced AccÃ¡ttoli), who is pretty good, wrote on 18 March that the Motu Proprio to derestrict the "Tridentine" Mass:
… potrebbe essere pubblicato entro Pasqua: il tempo «si avvicina» dicono in Vaticano, ma non c’ è ancora la data. Qualcuno lo prevede per il 25 marzo e altri per il 5 aprile, Giovedì Santo, che non sembra un giorno adatto per un testo normativo, essendo destinato a grandi celebrazioni. … could be published before Easter: the time is "drawing near", they are saying in the Vatican, but there is no date yet. Some foresee it coming on 25 March and others on 5 April, Holy Thursday, which does not seem to be a well-suited day for a normative text, since it is destined for great celebrations.
Another journalist, Marco Tosatti, who is much more on the conservative side of Church issues, wrote for La Stampa on 17 March that the document could come betweem 25 March and Easter.
Benedetto XVI «libera» la messa tridentina, la cosiddetta messa «in latino» amata – ma non solo – dai seguaci di monsignor Lefebvre, e per questo molto avversata dalle ali «progressiste» della Chiesa. E’ pronto il «motu proprio» del Papa, che dovrebbe essere promulgato fra la festa dell’Annunciazione (il 25 marzo) e la Pasqua. Il testo è blindatissimo; ma secondo indiscrezioni di ottima fonte dovrebbe rovesciare la situazione attuale. Benedict XVI will "free" the Tridentine Mass, the so-called Mass "in Latin", beloved by the followers of [Archbp.] Lefebvre – but not only them – and for this reason greatly opposed by the "progressivist" wing of the Church. The Pope’s "Motu Proprio", which should be promulgated between the feast of the Annunciation (25 March) and Easter, is ready. The text is highly protected ("blindatissimo" = "very heavily armoured"); but according to leaks ("indiscrezioni") from a very good source, it ought to reverse the present situation.
An "indiscrezione" is a comment made, literally, "indiscretely", that is by someone who is officially not supposed to be saying anything about the subject. Sometime enemies of the content of documents will leak something of the content in order to warn the opposition and stir up a pre-emptive fight.
Tosatti framed his comments with a description of the war on this document by liberal French bishops (who, btw, have about 2% Mass attendance in their dioceses… but I digress), thus giving a reason for the delay of the Motu Proprio. The delay reveals the Pope’s willingness to listen to dissenting views and consider them. Do not forget that it was once reported that Pope Benedict himself called by phone one of the key bishops opposing this move.
Tosatti suggested that if a minimum number of 30 people expressed desire for the older Mass, the bishop would be really be in a position to deny it. I am not sure what that means, in concrete, terms, but there is that number again.
Tosatti also reports that, in spite of the opposition (maybe because of it?) Card. Castrillon Hoyos (Pres. of the Pont. Comm. "Ecclesia Dei") says the Pope is now "decisio". He has "made up his mind".
Accattoli made a point I have been talking about in various posts over a long time: I don’t see His Holiness, who is very liturgically aware, issuing a document on a feast so that it would pull all attention away from the feast itself. Sign a document, yes. Release it, probably not.
Thus, the week following 25 March is a better guess. This is in keeping with things I have also heard. This is in keeping with what Tossati wrote.