I've seen it happen (also seen it not happen a whole lot more often) but you never know.
But here's some food for thought: Incredible is the king of the hill on Verizon right now (with Moto Droid a close second) but in 6 months (when they will almost certainly let you upgrade as long as your calling plan is high enough and you are in good standing with billing) there will be a new powerhouse Android phone that blows the Eris, Droid, Incredible, AND Evo out of the water.
Are you really THAT dissatisfied with the Eris with 2.1 or are you just chomping for something newer and better... if you are that dissatisfied with the phone them by all means to go the mattresses with it but if not sit tight for a bit and get something even better