I'm sure that is a strong possibility. That is exactly how U-verse works today, effectively. The DVR STB is the main device, similar to the Satellite IP server, that receives all of the video streams whether it is watching on a locally attached TV, recording or playing on another STB. All the other STBs just feed from the DVR over Ethernet. That is how the whole house DVR functions anyway. All video streams through the DVR and each STB just controls the particular stream it cares about via the DVR.
I think they would have to offer an 8 HD stream solution for customers with more than four TV's. I wonder if having an IP dish on the roof would do the same HD quality that the current DTV dishes have? Would it essentially be an Ethernet cable coming from the LNB to the server?