I know there are ways to get this now on the G1 through ROM cooking and rooting, but it will be nice to see an official T-Mobile OTA update come to G1 owners. I do have to wonder how well it can run on the G1 given the limited amount of memory and the 528MHz process on the device. I have been happy with the 1.6 update that gave us Google Maps Navigation so this would be even better to see first generation Android owners getting the latest operating system, similar to iPhone user experiences. I actually had a few relatives showing me their G1 over Christmas dinner and they were very happy with their Android device.
I will update this post if we can get some official T-Mobile confirmation of this upgrade.