He certainly is not going to fight until his baby is born in late August. TUF taping and the camp for the first DC fight took him away from being around to help his wife during her first pregnancy, and no way is he missing/getting away with that again....
He seems to think "of course" he'll get the rematch, but even if that doesn't happen immediately there's plenty of possibilities. Whether Ngannou ends up fighting Jones or Lewis, if he wins the loser would be someone new to Miocic. (In fact, what with the latest UFC roster purges EVERYBODY in the top 15 other than Ngannou would be a new opponent.) Blaydes would be a cool pick too; for those that pine for narratives, the angle of him being a training partner for Stipe on his camp for Gonzaga would make for interesting speculation. As would Volkov, to settle the nagging trollish question of whether excessive height is Stipe's kryptonite (see: Struve.)
Of course it's possible he might go on strike until he gets a title shot like he did with DC, but someone I don't think so. There's a difference in urgency between being 0-1 against a guy that's swearing to retire in a few months, thus taking away any chance at avenging your loss, and being 1-1 with a guy who's said he plans to stick around for at least 3 years.