Generally, exchanging doesn't affect your contract start date, so you may not need to extend out, but Verizon doesn't have a pre-determined one-year contract price set for the Charge, so you might run into some trouble.
Thanks for the info. I thought I read somewhere that they will be keeping 1 year contracts open for certain account types. I could be wrong. I'll be there tomorrow so when I find out I'll post back!