Andrea Tornielli on his blog for il Giornale has a glimpse of an interview with the Cardinal Secretary of State, H.E. Tarcisio Bertone, to be published soon in the weekly La Famiglia Cristiana. Card. Bertone mentions the instruction on Summorum Pontificum which will be issued by the Pontificial Commission Ecclesia Dei.
Here is my translation:
Concerning the Motu Proprio about the Tridentine Mass: "There are plans to fine tune an Instruction which will settle clearly the criteria for the application of the Motu Proprio. There have been some distorted reactions. Some even got to the point of accusing the Pope of having renounced the teaching of the Council. On the other hand, there are those who interpret the Motu Proprio as authorization for the return of the pre-Conciliar rite only. Both positions are wrong."On the other hand, there are those who interpret the Motu Proprio as authorization for the return of the pre-Conciliar rite only. Both positions are wrong."
The instruction, I am told, will probably come out before Easter. The first part will no doubt deal with overly restrictive interpretations of the provisions of the Motu Proprio.