No one has yes or no to 2.0 on the G1. However us with rooted G1s and T3Gs have recieved parts of 2.0 and are getting more soon.
Cyanogen is the only way to go. Read this link.
Read that link over and over again.
Read it a few more times. Make sure you have read it a few times.
Did I mention that you need to read that link.
Everything you need to know about rooting your phone is there.
Read this link again.
Once you have gotten to a point where you think you know what your doing, read a few more times.
The reason I say read it so much, is it makes it easier to keep track of where you are while rooting. Its alot easier than it looks. I have done 3 G1s and walked 2 mytouch3g people through doing it on a land line.
Once you are sure you understand what you have to do, go for it.
When done go to the Market and download the CMupdater so you can get the updates easy.
Feel free to PM me or post if you have questions.