No word yet on a CDMA 680, but we are expecting an announcement sometime soon. After all, this was supposed to be the affordable Palm. The one for the masses. . . . GSM only won't cover very many masses . .
Worth the upgrade? You will have to make that call. I recently put together a table with all the current Treo's on the market, to use for my own benefit. You might find it handy to compare the 650 to the 680 . .
http://dukecarico.com/Palmspec.htm