I recently demonstrated the new Pocket PC and Smartphone emulators as part of an MSDN webchat, and was asked by a participant if the emulators supported external USB devices.
At the moment, the answer is "no", but I checked with the feature team responsible and they said.. well they said a lot of interesting things that I can't repeat here. They did say that officially "they're thinking about it", which is - I know - not all that helpful, but at least it is promising 😉
However, they were really interested in what kind of devices developers needed support for. So if you think you would make use of USB support from the emulator, either email me or add a comment with the kind of device you would need support for, and I'll pass the information directly to the emulator feature team.