It should come to no surprise that the HTC Dream can run Android 2.0 since its running a predecessor already but here it is, someone hacked it so it runs the same 2.0 version like the new Motorola DROID.
Rather than hacking it, I would say to wait until upgrades are available from your wireless network carriers, I am sure Google will have the upgrades available soon for all Android-based smartphones including the G1 phone. (Then again, I guess updates might not be available unless you hack it for older Anroid phones. Why? I would certainly believe it would be easy to upgrade if Android is linux-based. OR maybe… keep your fingers crossed and subscribe to Zedomax.com until we have the good news.)