We don't know when this future will be set. It may be "some alternate future in the not too distant past," along with some prologue explaining how this all came about. DoFP is supposed to be a film that is its own thing. While I would put my money that this story follows the timeline from TLS, it may very well be some alternate timeline, and there is evidence to support both scenarios.
Originally Posted by X-Maniac
I think that 'fixing' things implies a lot more than simply following through with hints already left at the end of X3. If the cure doesn't work, and Xavier survived, then there's no need to 'fix' those things.
Surely it has to be something more radical than that.
Think you are reading too much into it. It could be minor details. Take the cameo of Hank in X2. Hence the image inducer in 1973 explaining his human appearance. He could simply be referring to small inconsistencies, rather than a complete overhaul of the OT.