I see two possibilities here:
1.) Levada and Fellay in their two hour discussion already came to a verbal agreement the Society could accept. The Pope wants to look hardline to appease the leftists so he has Levada issue the "ultimatum" and libs are happy. Notice the deadline is on Divine Mercy Sunday in the NO. In an act of "mercy" BXVI will accept Fellay's clarification.
Thoughts? Naive on Pope's part. Libs will still raise Hell no matter what. PR nightmare for Conciliar Church. Some extremist libs will leave Church. If Fellay accepts, BXVI will pull a fast one and probably announce the next step in JPII's canonization on the same day of Society's regularization to appease the left and reinforce the idea that both JPII and the Society are Catholic in some Hegelian mind meld.
2.) Rome is serious. It's either accept their liberal re-formatting of all Catholic thought or you're done. No room for Traditional conception of Tradition, ecclesiology, etc. from SSPX (even though Prof. Giardhini, Bishop Schneider share the Society's view and are still in "full communion.") SSPX refuses. SSPX is declared schismatic, excommunicated. All laity is warned they are excommunicated if they assist at an SSPX Mass.
Thoughts? Game on. Battle lines drawn. Clear choice. Time to choose. If JPII is eventually canonized, Fellay may recognize the fact that BXVI is a formal heretic, reach out to sede world and any Novus Trads who are willing, to elect a new Pope.
Conciliar church will eventually shrink, die off and disintegrate. More and more conservative Conciliarites will see the Society (or real Catholic Church at that point) growing and thriving and defect from Conciliar Rome. Conciliar Rome will be left with more and more libs and go completely off the rails.