According to
Brighthand MS will be releasing an update to WM5 in the first half of 2006, codenamed "Crossbow." It will probably be Windows Mobile 5 Second Edition, or WM5.5. I hope we don't have to wait that long for all the problems to be fixed. Plus, I bet only the X51 line will be offered upgrades and it will cost another $40.
This is all my speculation, but follows the previous pattern of MS and Dell.