Wouldn't say all that.
Great rappers still sound great if they collab with him. It's not like he's SO amazing that no one else is good.
That being said, I feel his career could go either way at this point. He could continue to bring the A-Game, or he could drop off. It's the same with every rapper, though. We never know how or what a rapper will do after their last album. KanYe for example. Dude released a dope album. And then he did 808's and Heartbreaks, and then released one of the dopest albums of 2011.
You never know how good an artist will be until they release their next album.