According to this New York Times article Microsoft plans to roll out several new tablets at the Consumer Electronics Show opening January 6th in Las Vegas. Most observers have been disappointed in Microsoft's showing in the mobile area. Their Win Phone was announced, cancelled and then re-announced this summer. Windows Phone 7 OS based phones have had limited success. They have been announcing tablet computers since 2001 so it's not surprising there are skeptics.
Most of the debate boils down to which operating systems will win out. With Apple iOS and Android having wide spread adoption, can Microsoft convince people that one of their two operating systems - Windows 7 Mobile or Windows 7 (PC version with touch screen) - can be competitive. We'll know soon. The train has left the station and unfortunately for Microsoft it's high speed rail this time and not the lumbering freight train of the 1980's PC revolution.