It's a good thing for the Bolsheviks. Not sure who'll lead certain battles of the Revolution in his place, but he was never totally indispensable to the effort. The only real question is who'll replace him as leader of the Right in the Politburo - probably Zinoviev or Bukharin (assuming butterflies don't kill them), would be my guess. However, it is likely that without Stalin's influence Trotsky could overcome the opposition to his taking power.
Insert Trotsky timeline, whether for you that's a Eurasian Sovietwank, Socialist Utopia or Fascism/Capitalism taking Moscow by 1940. That debate never really has been settled to anyone's satisfaction, I think.