Up till a week ago, that's what I had. I had that set up for two years and I just got the iPhone. I don't miss carrying two devices around but it was a lot cheaper.
You have two options if you want to drop from two device to one single device.
1) Buy an unlock iPhone5 for more than double the cost of a iPT5.
2) Buy a subsidized iP5 for $199 and then pay the ransom money to the carrier later.
Neither option is attractive.