I heard the same thing. I also heard his tour was rescheduled/postponed and will resume after he's back on his feet. I know age sometimes has nothing to do with it but he's still somewhat young for this kind of procedure, no?
Williams was a boozer and a cokehead. Coke helped him to calm down and escape into more of a quiet time (unlike most who get all amped up). After Belushi died, that scared him into going cold turkey, about six months after his son was born. I lived in Reno and saw him at a dumpy little club called 'Lips', about eight miles off the strip on S. Virginia Street. A friend took me to see this 'nobody' comedian at this dive and he was pretty darn funny! This was in 1975, before Mork and Mindy was launched.