if we plan to include new classes and have E_STRICT (imo not notice) to inform about the inclusion with the next minor version update would be a good thing. To stay with the example at hand, inclusion then would go like accepting Zip during 5.2 phase. Adding the E_STRICT at the point the decision was done and then in 5.3 do the actaul inclusion.
I agree this is a good idea. Although after 5.2 we could think about some core class names and mark them all as E_STRICT even if they wouldnt be included in the 5.x series. I think Pierre mentioned starting a new thread to look at what names PHP would like to reserve, I think it could be a good idea to start this sooner rather than later. Regards Marco