As if you needed another reason to hate cell phone contracts. For the last few years, Verizon's upgrade cycle has been 20 months long - that is, you bought a new, discounted phone on-contract, and you could upgrade after 20 months. (Not to be confused with the cellular contract itself, which is a full 2 years/24 months.) According to an official statement from Verizon Wireless, customers now have to wait the full 24 months before upgrading.
Here's the relevant text from the announcement: