To all that have 650's like me as well:

I will be doing both. Purchasing a 8700c on Cingular. And keeping my 650...for now.

I will carry and use the T650GSM and BB8700c in tandem until I need to not carry one anymore. Until one proves to be dead weight...and it will probably be the Treo.
I think I may actually get rid of the Treo 650 and get a Palm or WM PDA with a camera, that I can leave behind at will. Like a Zire 72...I would keep the T650 as an all around multimedia device, but the frickin' headphone jack broke (that would never happen on a BB!) so no go for movies or music. I wish the Palm T|X had a camera. It would be perfect to complement my new BB8700c. I don't want a camera, or SD slot or any of that on my main device (which will now be the 8700) because I want stability and email and voice first and foremost.

Hail the BB. Love my Treo 650, but the stability issues are no more. I am leaving for better pastures; namely, the 8700. As I said, though, with some sort of multimedia-centric PDA in addition, though.