He did not want out.
The line in GF II sums it all up when Tom tells him he's one and asks "do you have to wipe veryone out?" To which Michael replies "Only my enemies."
In other words as long as he had enemies, Michael was willing to kill them. That's hardly a man who wants out.
The only mobster who ever really wanted out was DeNiro in Analyze This.
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
"I stood in the courtroom like a fool."
"I am Constanza: Lord of the idiots."
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