I was a current T-Mobile customer, and I was still able to get two of the phones for the standard $179/each by renewing my contract. If you don't want to deal with contracts, you should expect to pay much more for your phones anyways...
No, I was only about a year in from the last point at which I had renewed in order to pick up the MyFaves plan. However, I am on a family plan for my wife and I, but I can't imagine that changes much. Just try going to your local T-Mobile rep and asking about the G1, and see what they say.
