The South Stand was last renovated in 1983, the South Stand (or The Sir Bobby Charlton Stand) is now the smallest and oldest of the stands at Old Trafford, with seating best described as fairly cramped and It backs onto a railway line.
The club could build over it. But that would likely make development expensive. It has been estimated that redeveloping the South Stand alone may cost as much as Ł750m and apparently the Glaziers have spend nothing on the stadium for 15 years.
A big job is needed on the Theatre of Dreams to bring it up to standard.