IMO the team would be foolish to just let him walk. I wouldn't give him anything beyond a 1 or maybe 2 year deal at maybe $6-8 million per year though. If a team is willing to give him a multi year deal beyond 2 years at $10+ million per year than so be it, but I wouldn't just let him walk. When healthy he is the second best center in the league and when you team him with an all-star in Holiday and other emerging young players you actually have something. Granted, I don't think he'll ever be able to play a full season, but as VanillaThunder3 mentioned, if he proves himself on a one year deal than you've done your homework.
Even with this debacle I still really, really like this 76ers roster with Holiday, Bynum, T. Young and Turner. I really don't know what happened this year, because I thought even with Bynum being out this team should have won 45 games at least.