If Don Corleone had agreed to Sollozo's deal, would the Corleone Family have been better off in ten years
...like Tom Hagen predicted and thriving with everyone still alive?
We don’t know. It’s possible that Barzini would’ve came after him anyways
But I lean to thinking yes - Vito’s rejection of narcotics was grounded in the values of yesterday, where there was more morality in society. Society was changing and becoming more decadent. Vito’s rejection of Sollozo’s deal was basically signifying that he was aging out and therefore losing his touch
I always assume that Barzini knew in advance that Vito would reject Sollanzo’s offer anyways