From what I've been hearing, the days of unlimited data plans - and quite possibly, any & all unlimited plans will soon be over (when VZW switches to LTE/4G). And if that's the case, than the hell with 4G, I don't want it! To have to worry about, & monitor usage again is such a huge step backwards!
Verizon's "unlimited data" is already limited... Anything over 5Gb will get you a nasty warning... Do it consistently, or go WAY over, and your service will be cancelled... It's in your contract (if you read the fine print).
That being said, now that AT&T have brought in tiered services, I'm betting VZW will follow suite. BUT, they'll probably always have an "unlimited" plan to set themselves apart from the competition.