My guess is this is just a rumor and it's not coming out. But if it really is coming out, a few things:
-Don't call it MMLP 3, especially if it doesn't sound or feel anything like the first one. The second one should have been called something else entirely, because it had almost nothing to do with the first one outside of "Bad Guy." Eminem has said multiple times that he sees the MMLP as his best album and he's still chasing it, so why would he think putting out unnecessary sequels would help? It didn't make sense when Jay-Z did it, either.
-I highly doubt Rick Rubin or Alex da Kid would produce anything, especially after Revival. Eminem knows better in 2021 not to do 2013 shyt. If anything, guys like d.a. got that dope or Illa da Producer will be on this. Dre should be on it too, Eminem will co-produce with Luis Resto and there will most likely be features from younger rappers.
-Skylar Grey's going to be on this, isn't she?