I agree Vito would have gone to Nevada, and lived with Mama on the compound. He would do his gardening and don't forget he liked to go fishing also.

It is telling that in the Moe Green scene Tom makes it explicitly clear that the Don is "Semni-Retired" and tht Michael was in charge of the family business. My guess is Tom started taking the "semi" out of it when he spoke about the family after that. For sure when he was in Vegas laying the groundwork for the move he made it plain to evryone that Michael was now the boss. In fact had he lived, my guess is he would have gone to the safety of the Tahoe compound before the massacre.

This should have been a "tell" to the other families that Vito could keep his pledge, but that Michael was not bound by it....EXCEPT...Michael brilliantly hid the true strength of the family, nd no one knew how powerful they were, nor how strong Michael was. Reminds me of another Pacino movie "The Devil's Advocate when Pacino advises that it is better to be underestimated, and to "never let them see you coming."