It doesn't really solve the fundamental issue that Barzini wants to take a run at the Corleones, does it? I think Barzini bides his time, and tries to become the dominant partner in the drugs business, by turning Sollozzo and Tattaglia against each other and then picking up the pieces.

I think Vito would have two sometimes conflicting goals: (1) to try to get the Sonny/Tom leadership pair up and running; and, (2) to try to accelerate (because he thinks the drugs are suicide) getting the family into legitimate businesses. Sonny would, of course, want to continue and extend the Family. I think Michael would finish his schooling, and then Vito would wow him with a "legitimate" job offer that he couldn't refuse.

Eventually, there's a Barzini-Corleone confrontation. Barzini would rather have that after Vito is gone, but I don't know if it could be put off for that long.