Back in my sales days, we called that tactic "SWAT" ("Sell What's
Available Today!")  The idea is that they have you on the phone NOW, and
have a better chance of selling you something while in contact with you,
rather than hope you call back in a week or two when the "new product" is
released.

From T-Mo's POV, they already have the Dash Smartphone with WM6, so they
already had something in the WM6 category to hook you with, rather than
address future products that might delay your purchase.

Well, to be fair, the Wing was released ahead of schedule (I suspect
their supply of the MDA, the previous model, didn't last as long as
they'd hoped!) and apparently T-Mo had some relatively last-minute
internal bickering about the name.  Often the CSRs are left in the dark
about new products- a sort of "forced SWAT" tactic- the less they know,
the less they can unintentionally delay your purchase with future product
info.  (Picture a car dealer with a lot full of 2006 models when the
2007s are released- the salespeople go out of their way to explain how
nothing of importance has been improved on the '07, and point out how
much cheaper you can get an '06 while supplies last.  Until the '06s sell
out, that is.  From that point, they'll explain that the '06 was a total
piece of %&!* and the '07 is a ground-up redesign!  ;-)

The Wing, while a cute device, offers no significant new features over
it's MDA predecessor, save that it's a WM6 device instead of WM5.  As a
happy MDA owner, I'm holding out for whatever they replace the Wing with
later this year (hopefully) when they launch 3G UMTS/HSDPA data.

Because when the call centre staff receive their new phone information it
comes along with "Embargoed until xx" stamped across it. 90% of the industry
are already discussing Tmobile's 3G system about to be sold in the next
month or two but good luck in finding anyone in Tmobile willing to discuss
it, even though staff are now going on in-house training