At the end of this year, when the first Windows Phone 7 Series phones will be in the stores, they will all look the same. At launch, WM7S will mainly just support 1 formfactor. There are plans for two other formfactors.
During the MWC we could mainly look at the prototype with Windows Phone 7 Series. We were not allowed to play because it was not fully functional. Landscape modus for instance. Even devices with a full keyboard were not yet supported. Evenmore, when the WM7S is in store it will be supported by just one formfactor; a full touchscreen called 'Chassis 1'.
It's all got to do with Microsoft's renewed strategy not to support too much hardware. But, only one chassis that's a tad bit underdone. Support for other formfactors is in the making.
Windows Phone 7 Series demo
Chassis 1, 2 and 3
Chassis 1 actually is a spec which Microsoft prescribes; complete touchscreen, 1 GHz processor and a GPU (graphic processor). Chassis 2 and 3 to follow later and have a physical keyboard. However , at first we'll have to do with a full touch phone. Thinking back at the WM7S demos we'll accept that.