Dahak
Explorer
So that's their strategy to generate the "fresh core book" sales spikes for 5e? Well, in 4e calling them PHB 2, 3, etc. failed and people saw them as the splat books that they are rather than real PHBs. I don't think this new approach will have better success.
I suspect the Adventurer's Handbook will be more like HotFL or HotFK in that it serves as a standalone PHB alternative. If Part 2 is reprinted in whole, and classes each have new subclasses, new assortment of spells, with only a few key reprints, it might work. Elemental Evil would effectively be a standalone game that is fully compatible with the core.