The new BD from Shout is going to recycle the MGM master with their worse compression like they usually do. The big news is that they may produce new extras-and better yet that Arrow is doing a uk release with their high level of quality- so expect the MGM master from them with better compression and original audio and new extras.
The current MGM release is as good as it gets and could only use the original 2.0 track and feature the extras on the BD instead of only on the DVD. The 5.1 mix is faithful and is virtually identical to the original as far as I can tell and the transfer is about the only one Friedkin hasn’t fiddled with.