Michael is very cold and methodical in combat, but I don't think he is the kind of guy to betray his friends. He, MC, and Alice have developed a very deep camaraderie and friendship throughout the game, and they have a very high level of trust in each other. They basically don't have any secrets, I don't see Michael betraying them. It wouldn't be in his character. I also don't see how it would be advantageous because they are small fish in a big pond and the fact that all three of them can trust each other, all have powerful abilities, and can all grow together is a huge benefit. Grouping up and having a reliable squad is a huge advantage in this kind of thing vs going off on your own. For mc I think thats been a theme throughout this game as well, that he needs to make friends and build up his allies and connections if he wants to survive all the crazy shit thats going on and stand up to Ella. Even Ella has her own band of underlings.