Rumor has it that there will be very few chassis designs available for Windows Phone 7 Series, with only 1 being available at launch. At the big announcement at MWC, Microsoft did say they were going to put more hardware restrictions on the manufacturer. Chassis 1 has a full touchscreen, gigahertz processor, and dedicated graphics acceleration (perhaps without a hardware QWERTY keyboard since that’s in the Chassis 2) and is rumored to be the only version available at launch.
Chassis 2 is rumored to be more like the Palm Treo series, with a dedicated QWERTY keyboard. Chassis 3 is unknown at this point, although speculation is leaning towards a candybar style.