After my post this morning, Landline, Skype, or both with the DUALphone 3088, I've been contacted directly by Skype about dual mode phones coming on stream that will support multiple handsets.

There were two products announced at CES. The Netgear SPH200D looks promising, supporting up to four handsets (the SPH150D) and providing the same landline and Skype support using DECT internally (rather than WiFi).