I wouldn't trust the Amazon specs at this point. They still have many blu-ray titles listed as having only AC-3. Plus it is early with no official release date yet...I doubt the studio has released full specs yet.
I doubt it will be 5.1 as the BD TE release was 6.1. The DVD set went from 5.1 to 6.1 for the EE, so I would think 7.1.....but at least the same 6.1 as the BD TE.
As for the special features, I might be one of the few who has watched ALL 6 discs several times over
So I would like to see them in HD on BD. At very least, scale them properly and condense them down to one disc per movie instead of two. I think the minimal special features that came with the BD TE set were on BD discs.....though I'd have to check to see if they were still in SD or not.
Most of all, I truly hope that they get the transfer right this time. The BD TE's were still much better than the DVD's and they get better through the trilogy. But I miss the EE's and I would like to see them done right.
I do wonder about the use of the word "Limited." Are they saying that this is a limited edition release....or that set has only limited extra content compared to the next set that could be released after the hobbit films