The Cupcake may not have been released yet. But now, you can get most of the goodies in the package, for your T-Mobile G1. The most important ascpects of the Cupcake, like the on-screen keyboard, video recording, updated browser, etc. can all be downloaded to your T-mobile G1 now.Its available in two versions : the G line (Google sourced) and the H line (HTC sourced). But the users who ported the G line to their device have been blocked from the Android Market. And the reason is that the G line, when registered on Android Market, showed as Magic, which has not been released yet.
The latest versions of both the ports can be downloaded here.