Hi Pilgrim,
I must admit I use my no name DECT phone in the analog port of the UC320W. It behaves like any other analog phone with pretty good range. The 792x will not work now or in the future on the UC320W.
Check out the star codes support and flash hook support for analog phones in the attached user guide, page 70..
There is mentioned by Bassanio in the URL below "We have a mobile handset program on the roadmap"
https://supportforums.cisco.com/message/3331190#3331190
So do expect something, but if you are waiting for a DECT handset before you buy a UC320W solution, don't wait.
regards Dave