I'm surprised that there still hasn't been a Follow That Bird Blu-ray now. Elmo in Grouchland I'm a little less surprised, though I could see Sony doing that (since Sony did release the first Blu-rays of Muppet movies). Next year would be the 20th anniversary of Elmo in Grouchland, that would make a good time to put out a Blu-ray (if they thought the anniversary would be worth celebrating). Putting out Blu-ray editions of either movie would also be a good way to tie in with the shows 50th anniversary.
Suddenly, I wonder if maybe Warner and/or Sony were waiting for that announced-but-not-guaranteed-to-be-made third Sesame Street movie to put out Blu-rays of those films.
I could see Blu-ray releases of the stuff shot in HD, but putting out works produced on tape wouldn't improve on HD. I wonder if they could market an "HD Sesame Street" collection (what would make a good title), or maybe just a release that would stick with HD-produced segments. Of course in the last few years most Sesame Street DVD releases have only contained material shot in HD (not counting bonus features). Maybe they could put out a "complete" compilation for Elmo the Musical, Abby's Flying Fairy School, Super Grover 2.0, Cookie's Crumby Pictures, or Smart Cookies on Blu-ray.