imo, any such expansion should be theme based, therefore the title should reflect that theme. Something like;
- Players Options: Giants
- Combat Options
- Rogue's Companion
- Greyhawk Players Companion
- etc
Something like PHB2, other than the previously mentioned issues, doesn't tell me WHAT it adds to my game. The names above do.
Eberron Adventurer's Guide? or some other book(s) akin to SCAG. Crunch alongside story/background material.
Maybe more FR related overarching regions. The Ancestral Barbarian could be originating in Kara-tur.
Really hoping for the Eberron book alongside Psionics for 5th ed.