Brighthand reports that the Treo 600 has received FCC approval, in GSM and CDMA variants. According to the initial Treo 600 reports, the CDMA version is due from Sprint in October. There is still no word on when, or which, US carriers will offer the GSM version (Orange will offer it in Europe, timeframe unknown).
I’m now convinced that the Palm OS offers the best platform for converged devices in the near-term, and the Treo 600 appears to offer a combination of PDA, phone, and e-mail functionality that is unrivaled by any other device on the horizon. The low-resolution screen is a bit of a turn-off, and I’m still wary of phones with exposed touchscreens, but I’ll be the first in line to buy one anyway.

I am a happy owner of a treo 180, for me the keyboard, low res and exposed screen are too big nuisances to accept this new baby, I would hope to have an updated sofware for mine.
From the propaganda that Handspring has been sending me about the Treo 600, it appears that they have put much thought into how to shrink the keyboard without sacrificing usability.
Updates for the current Treo models are unlikely — no Flash ROM.