Sun Wukong had absolutely no problems when MK found a new friend. It's just great that his successor is socializing! As a good mentor, he is satisfied with even the smallest of his student. And so, the day of their meeting came, and Wukong was puzzled to say the least.
No, MK's friend wasn't bad, he won't be able to say that even in jest, because it's an absolute lie. But there's still something wrong with it. Standing next to them, Wukong feels something, as if there is some kind of aura in this person. Not a deity, and not a demon, as if something in between.
Wukong can't figure out if this is a good thing or a bad thing. He just can't figure out which side to look at, maybe there's some kind of power hidden in them? The power that he could feel? Or something else? It had been a long time since he had thought so much about something.
In fact, on the same principle, he chose MK as his successor, just feeling it in him. Yes, that's right. He just felt that it would be the right decision. Yeah, it sounds a little absurd, but Monkey King still made no mistake in his choice, his intuition turned out to be correct like never before.
But here the situation is a bit different, he knows that. Wukong knows all the prophecies, all the legends and scrolls about the "future", he lived at the time of their creation, and he couldn't say that this was one of them. Maybe he's just getting old... Yes, that's probably true.