According to popular opinion, it's when you upgrade your phone after this summer.
Recently Google made it clear they're going back to selling unsubsidized phones, which seemed like a dumb idea to me, but then it occurred to me.
But thanks to SIM cards for LTE, I can buy a Google phone, swap in the LTE chip and keep my unlimited data while flipping Verizon the bird.
Apparently somebody is still doing it on AT&T and keeping there unlimited data
It's in the mess comments in this article.
Verizon Statement on Unlimited Data: Will Let You Know of Policy Changes When We Get Closer to Shared Data – Droid Life
Granted, this means paying out the nose for an unsubsidized phone, Verizon can blow me.