They'll go back to the negatives and remaster this bat boy for HD. The Green Hornet ran on SciFi a while back, and looked good as new. Hopefully, that's in the pipeline too.
There's money to be made in new HD syndication masters as well. (A factor that drove Paramount to spend big bucks to remaster Star Trek TNG.) Fox won't have to rebuild the episodes from scratch. I don't recall a lot of songs that would be a licensing problem.
I don't see celebrity cameos being a serious problem, unless it involves the estate of one who's difficult to deal with. (Sadly, a lot of them have passed away.)
"In character" cameos like Lurch and Col. Klink, might be tricky, since those characters are obviously not owned by Fox or Warners.
All cameos in one youtube video.