Verizon Unlimited Data and New Contracts

I'm on an unlimited data, unlimited text, and 450 minute plan from Verizon. I was grandfathered-in to the unlimited data. My contract 'ends' in December. The discounted upgrade starts in August. If I don't buy a discounted phone from them, can I renew in December and keep the unlimited data? Or will I have to sign a completely new contract with a tiered data plan? Thanks in advance.