As T-Mobile Germany just confirmed me, the carrier has no plans yet to release a Windows Mobile 6 ROM update for it's recently announced T-Mobile MDA Mail.
This makes me a kind of wonder since the T-Mobile MDA Mail is based on HTC's Excalibur reference design which the T-Mobile Dash is also based on.
However, contrary to the statement from T-Mobile "Europe", T-Mobile USA announced on Monday to release a free Windows Mobile 6 update later this year.

Too bad for European T-Mobile customers but T-Mobile might change its mind again.

Cheers ~ Arne