What little I have seen/heard about this suggests it's too early to think of doing it with a stand-alone unit. The price for Blu-Ray DVD-Rs I have heard mentioned is something like $8 a piece, so you better get it right the first time, if you can find a stand-alone recorder to begin with.
The best would be a Hi-Def harddrive recorder, like the Panasonic ones available now in regular def. Then one could always think of perhaps x-ferring selected footage to a Blu-Ray burner on a PC, but I have not seen such a beast out there, apart from the license models from the various cable tv providers. I say this with the caveat that I haven't researched it heavily of late.
Another issue is that some shows evidently now are having copy protection built in, much like DVDs, to prevent recording.
Maybe others have more recent info; I too would like to have the ability to keep Hi-Def shows from time to time.
C.