My understanding is that there ain't nothing wrong with 483 that can't be fixed.
However, the RR has had to make the very hard decision that fixing 483 is so much more expensive than the other engines of the same class that it is, at present, cost prohibitive.
C&TS president John Bush is VERY much a railfan and knows what an icon that engine is, but he still has to run a railroad!
If there are folk with VERY deep pockets that want to get 483 back under steam, my bet is that it could happen.
Oh....great....I used the word "very" three times (now 4) in the same post.
Cheers from Dallas TX
Clyde "verily" Putman