Popular AOSP-based custom ROM CyanogenMod will discontinue support for the T-Mobile G1 and its keyboardless sibling, the HTC Magic (aka myTouch 3G) after the current version 6.1. This means that there will be no official version of the Gingerbread-based CyanogenMod 7 for these devices. However, this doesn't rule out the possibility of an unofficial CM7 community port for variants the G1, which launched way in October 2008 as the first Android smartphone.
It's likely that the anemic 192MB of RAM present in the G1 and most Magic-based phones, combined with dwindling user numbers, was behind the decision to cut support after CyanogenMod 6.1.
Being stuck on CM 6.1 isn't such a terrible fate, though, especially considering that the G1 never saw any official updates beyond Android 1.6 from manufacturer HTC. CyanogenMod 6.1 is still an excellent ROM, and should serve G1 and myTouch 3G users well in their handsets' twilight years. [CyanogenMod via reddit]