After all of the Treo WM rumors that keep reappearing then dying down, I think the following is becoming pretty clear:
1. Palm, while maintaining an "OS agnostic" official line, flirted with WM on the Treo for a "just in case" scenario, just as Apple has been compiling OS X to run on x86 since day 1.
2. Palm has decided that while WM might get them new customers in the short run, they've decided against it and are now completely behind Linux. Whether or not it's a way of preparing their devices for the arrival of Palm OS for Linux from PalmSource, or they are developing their own OS using Linux (as Bob suggests) remains to be seen. It wouldn't surprise me, especially if it's combined with some software from Jeff Hawkins's & Donna Dubinsky's latest startup
Numenta, which is developing software tools and an OS using "real intelligence".
Brian