Walt brings Mike's body back to the pest shop in the trunk of his car. Todd is there and Walt says something like "it had to be done. I don't want to talk about it." Todd is like okie dokie and then Jessie shows up while Mike's body is still in the trunk. I can't remember if they actually showed them dissolving the body but I think it was implied. Walt would never just leave Mike's body to be discovered.
I have a feeling someone will tell Mike's daughter in law. It seems like there is a lot of symmetry between the two story lines with Nacho. Also, the police are almost certainly going to question the daughter in law after they are unable to find Mike in which case she will find out he got mixed up into something bad. I can't remember, but I'm not sure if the daughter in law was ever in Breaking Bad? Either way she is in Better Call Saul and had more than just a bit role so I think they will tie up that loose end. I have a feeling that the daughter in law will be on TV because there is a manhunt underway for Mike and she is pleading for Mike to return and/or whoever knows what happened to him to come forward, and Saul feeling guilty, decides to tell her or somehow get a message to her.