You're not locked in for another 2 years. Even on a 2 year service agreement, you were never locked in. As long as you're willing to pay what is required to get out of the agreement then you are free to do whatever you like. The difference is, with DPP you can pay the balance on the device and get a new one. With a 2 year service agreement you can't pay the ETF and upgrade, you have to wait it out to upgrade and stay with VZW.

Why would you buy the new phone and plunk down all of the money upfront and keep payments on the old phone? Why not just pay the balance of the old phone and get the new one on DPP?