I've learned that there is absolutely no rhyme or reason to when Verizon will allow you to upgrade.
In theory, the concept is "New Every Two," meaning you'd be eligible every two years for a phone upgrade. I believe the upgrade consists of offering you $100 off the 2 yr contract price for a new phone, and extending your contract for another 2 years.
The reality is that they will often allow you to upgrade earlier than the 2 year mark...but I'm not entirely clear how early that is. Verizon can pull up the 'earliest' date in the computer if you stop in and ask.
When I say there is no rhyme or reason...it's because I found this past November that there are literally thousands of stories on the internet of folks in a variety of different situations who were able to upgrade early to their DROID.
In my case, I wasn't eligible for my 'New Every Two' until September of 2010.
When I asked at the store on a couple of different occasions...I was consistently given the September date as my earliest possible upgrade.
Reading various postings on the internet, however, I discovered a wide range of folks who were able to call Verizon and by talking to different CSR's at different times...find one who was willing to upgrade them early.
I also read tales of folks talking to different CSR's in store...and eventually finding one who would upgrade them early.
In my case, I eventually called Verizon at *611 in November...and after a few minutes of hold time...was told that sure, I could upgrade to the DROID for $199 and they'd even do the $100 rebate instantly. So I got the phone sent free via FedEx for $199 and didn't have to pay $299 and wait for my rebate card.
So the reality is...you can definitely count on upgrading once every two years...but you might get lucky at some point prior to that.
I should point out that my previous phone was a Moto Rival...and there was a definite financial incentive for Verizon to allow me to go to DROID early, since I am now paying for a $30 data plan that I wasn't before.
I suspect that if I'd had a Blackberry prior...I might not have had as much luck convincing them to upgrade me early.