Here's today's news of the Microsoft/Palm collaboration on the Treo 700 with Windows Mobile 5.0, as hinted at in Businessweek last week. See also the announcement on Microsoft.com. (Update 101006: this is an old link: please see this link for more on Windows Mobile on Palm devices.)
"Full product details will be disclosed when the product is available for purchase in early calendar 2006. Palm indicated that a Treo smartphone using Windows Mobile based on other wireless technologies was not anticipated to be released earlier than the second half of 2006."
Waiting patiently until 2006... until then, I seriously am considering the Motorola Q Smartphone.