I'm looking at buying a house with a full DTV setup.

Including the Tivo HD DVR.

Can anyone explain what will happen when DTV launches the new
Mpeg4 sats? Will the existing setup work? Will I need to replace all
the equipment or just some of it? Will the DVR not work for those
channels in Mpeg4?

I know there is probably not a simple answer to all this so if anyone
could point me to a web site that discuses this I'd appreciate it.

no, you will not have to change a thing.