No, the Mazda6 is an all-new platform that is Mazda-only for the time being, but there should be some Ford/Mercury variants in a model year or so, apparently the Ford 500 and Mercury Montego.
We've all been hoping for some North American variant of the CDW-132 (I think that's the number), "new" European Mondeo, but it doesn't appear to be in the cards. Nor does any Volvo-based Ford/Mercury cars for that matter.
The CDW-27 (Original Contour/Mystique/Mondeo) platform lives on here as the Ford Escape/Mercury Tribute, but you could hardly call that an enthusiast/performance vehicle...
FWIW,
-Peter
(not driving his new Mazda 6 in today's rain and hating every minute of that)
04 Mazda 6s V6 MTX, in service 10/28/03

02 Subaru Impreza Outback Sport 165HP 4cyl auto AWD
former: 95 Mystique LS V6 MTX [11/14/94-5/19/04]