The next update for the T-Mobile G1 in RC33 has begun to roll out to G1 owners with the process expected to take two weeks. RC33 is meant to be a bugfix/maintenance release before the next major update known coloquially as Cupcake.
The update, as with every other G1 update is being sent out over the air in stages to every owner as to prevent network overload.
Encyclopedia: T-Mobile G1
When is the next update for the g1 gonna come to us users