Most of all, he isn't shocking anymore. He's not controversial. America has generally accepted him as the guy who will be a major dick and get away with it. I doubt he will ever again say something like "Fuck money I don't rap for dead presidents, I'd rather see the President dead, It's never been said but I set precedents."
All I can see him releasing is dope lyrics and punchlines. I think he will go from an amazing songwriter to strictly a lyricist. We will get a bunch of song-length Despicables. I'm afraid Eminem albums as we know them are over

Jay-Z has survived so long because he can adapt. He really has made himself "forever young". I honestly can't see Eminem adapting without putting out a bunch of pussy songs. I think Drake's great, but do I want to hear an Eminem version of Fireworks? Hell no. I