No, it'll come with it's own SIM inside. You call them to activate it, but they can switch your service, or add or upgrade to a new service, at the same time. Then the old phone can be deactivated if you want the new phone to get your old # and no longer plan on using it. Least that's what they did for me the last time I upgraded, and that's what the last rep I spoke with told me. I'm eligible for an upgrade right after it comes out, but she said something about having to pay "full price" if it didn't. They don't know yet if you have to sign a brand new contract, or can extend your old one, but I'm sure they have something they can do with existing customers who still have time left on their contracts.
No word yet on how they'll do it if you don't want a contract, or if you even have a choice.