Microsoft is supposed to show a new generation of UMPC (Origami, Vistagami, whatever you want to call it) at the CES 2007.

The new UMPC will be based of course on Windows Vista. The first generation UMPC, which are based on Windows XP have been way to expensive to be disruptive at any point in time.
I would be surprised if the Windows Vista based UMPCs will be cheaper. Ideally such devices which are not a notebook, but also not a PDA or smart phone, would be priced below $500. Current UMPCs are closer to $1,000. The Samsung Q1 sells for $899.99 at Best Buy.
More details on CNET.