I hate to say it, but I really wish Motorola would take a page out of Apple's (and now Samsung's?) book. Release two screen sizes for the Moto X 2015, something like 5.5 and 5", with identical hardware and slightly different battery sizes.
I'm still loving my 4.7" Moto X first generation, and although I want a new phone, I can't see wanting something bigger than 5". If they keep screen size at 5.2" and increase battery, I guess I will make do with that. Anything bigger, and I guess I won't be upgrading any time soon.
The "Mini" phones (Samsung S4/S5 Mini, Droid Mini, HTC One Mini, etc) probably don't sell a lot because the hardware is also mini. When will we have more flagship phones with two screen sizes?