As mentioned above, portability. Smartphones all round. Tablet PCs will become more promonant as the prices drop too. See Pocket PC 2003 and the Compact Framework.
Again, mentioned before, networking. Everything will be plumbed together to the extent that you'll be able to start your dinner cooking while sitting on the bus using, for example, your smartphone. Read up on Indigo in Longhorn.
Usability and making things look pretty. Read about WinFS and Aero in Longhorn... and watch the Real Estate demo video!!! awesome stuff.
However the biggest change this decade will be further integration of all the existing and new technologies in to every day life.. so my mother will take her tablet pc with her to the supermarket and cross off the shopping list on OneNote after downloading
the shopping from the web service running on her Fridge Freezer.