Anyone else think maybe that Desmond is aware of both (or all) timelines no matter which he is in? That is why he is special? Perhaps actually able to be in both the OT stuck on the island again and in the FST working for the Widmores but now with Penny as well (surrogate father approval and the woman he loves . . . whew . . . what a parlay!) Perhaps he can freely slide between or back and forth. The others (Jack, Sawyer, et al) will need to exercise their Free Will to choose in which timeline they will continue to exist. Does any of that make sense?