I heard that the MPx200 will be flash-upgradeable to SP2003.
But I don't have a firm source for that, and I don't have an estimated time
of availability either.
On the AT&T Wireless developer forum, a moderator recently (3 November)
posted this notice:
AT&T Wireless is actively exploring with our partners the opportunity to
offer a Windows Mobile 2003 software upgrade for the Motorola MPx200 phone.
Your patience is appreciated during this exploration period.
-Dino