According to AndroidandMe, every current Android phone will get Android 2.1, but some may require a wipe of the current ROM.

As stated in their website; “After talking with several inside sources familiar with the matter, I would like to report that every Android phone currently released in the United States will be receiving an upgrade to Android 2.1.

Some phones could be missing features of Android 2.1 (live wallpapers), but they will all have an Android 2.1 firmware.”

The  G1 and myTouch 3G will be the initial 1st gen devices to receive the update.