OK, bumping this thread to give you an update. The release date for these was September 8th and long story short, they seems to be appearing now because my copies are starting to arrive.
Anyway, I got the 45th anniversary edition of Frosty the Snowman on Blu-ray (got the DVD edition of both 45th anniversary editions of the specials) and I can confirm the transfer is the same from 4 years ago (there's some DNR present when Hocus Pocus is introduced, that's how I know. That and the Rankin/Bass Presents credit is still missing(!)) and audio is DTS-HD 5.1.
Now, some cool news; Frosty Returns has now been remastered in HD, this I can confirm! However, the video-generated effects look film-like now, no surprise.