I've heard of tweets going out that say the "Google" phone is coming to T-Mo in Jan but nothing that says the Passion. Besides most rumors declare the Dragon as the CDMA equivalent to the Passion. And most rumors about the "Google" phone say that HTC most likely isn't making it. Soo....
From what I've read, the GPhone was thought to be data only using VOIP and wasn't said to be tied to a specific carrier. Now T-Mobile is rumored to be the carrier. Too soon to tell for me.
If I had to guess I would say Gphone will go with TMO and will be made by HTC. Google is loyal and those were the two companies that gave google their first phone. But of course that is merely a guess so time will tell.
As of this morning it is still speculation that the Passion is THE Google phone and speculation it will be going to TMO. There is also the mysterious appearance a G1/Hero "clone" that may make it's way to AT&T with a snapdragon processor. That would be 2 on their network. If it happens.