I wonder how many backgrounds we will get in the PHB, because it does seem that each background is going to take a good chunk of page space, I don't think it's a page per background but might be 2-3 backgrounds per page if the font is small enough.
I can certainly see WotC or a 3pp publishing a book dedicate to backgrounds and the trait, ideals, bonds and flaws system, but I can also see backgrounds being published for AP and mini settings.
I like it, it seems interesting enough and it can promote more roleplaying around the table which, IMO, is good.
Warder