I have no problem with him recording things he's sung live before but hasn't officially released. Not everyone sees him live or has bootlegs of his shows.
I kind of get the feeling he's going to go old-school as well. I wouldn't be at all surprised if we get some Merle! In fact, this convo reminded me of a line from "They're Not Here, They're Not Coming":
"Well, it's a cold, cold, cold, cold, cold, cold, cold, cold
Post, postmodern world
No authenticity, no sign of soul
The radio won't play George and Merle"
So he's just gotta include a song by each of those guys!