Michael could not have known at that point that he would kill S&M. But it's a clear statement to Kay that, at least for the time being, he "belonged" to his family, and not to her--that his relationship with her would have to take at least a temporary backseat to whatever he had to do to help his father. So, in a way, you could argue that it marked the beginning of his move to Donship.
Thanks for the info everyone. I think what Turnbull said clears everything up.
I think you are correct TB, and I would add that Michael sensed that Sonny was not up to being a good Don. In the brief time after the hit, Sonny is out of control and not thinking clearly. Luca has turned up dead, and Sonny has ordered Paulie's execution in front of more people than he had to. I think Mike
was unsure how he would fit in, but his telling Kay that he now belonged to the family, and the brilliant instinct he showed by going to the hospital only to find his father unguarded sealed it for him. I think even if there had been gaurds around, Michael was going to the hospital to tell his father "I'm with you now, Pop."
There's no evidence that Michael sensed anything about Sonny. Sonny out of control? That is quite an exageration, n'est pas? Sonny gets the call from Sollozzo and acts prudently by placing both Clemenza and Paulie under suspicion. He gets the phone company to report on Clemenza's and Paulie's phone calls. He recruits Tessio's regime to replace Clemenza's and has them guard not only the house but the hospital also. Again, prudence.
His instructions about Paulie are in front of the top three people in the family and his brother and the instructions are ambiguous. Hardly a risk. I'm not sure why you bring up Luca's death as a function of Sonny's demeanor.
Mike went to the hospital almost as an afterthought. He did it late, after his date with Kay. That's hardly the behavior of one committed to his family. He didn't tell Kay anything about his intentions. It was only when he discovers his father in jeopardy that he tells him that he is with him now. However, that statement is undefined. What did he mean by it: that he was willing to take up arms; that he wanted to command a regime? I don't think so. He was simply expressing a familial love for his father and comforting him.
