Dontomasso,Wouldn't Vito have had the same muscle that Michael later used to take out the Dons? All of the shooters were available to him while Mike was enroute.
Not at the point when Michael would have had his "accident." The secret Rocco regime was not yet in place, and the family had suffered heavy losses in the war. Remember to keep the whole thing a secret, it took Michael several years to quietly rebuild the family's muscle, and during that time he had to be humiliated by Moe Green, and had to allow Barzini to chisel on Tessio and Clemenza's territories all without retribution.
Further, I am not sure that with Sonny dead and Vito as sick as he was that an operation as massive as the one Michael pulled off could have been done. All the family had was a sick and aging Vito who had pretty much lost it, Tom "Lets negotiate a deal" Hagen, Tessio (a traitor) and Clemenza.
Had Mike been killed,I wonder if Vito would have even had the heart to avenge him. Being the calculating practical type, he figures what's the percentage? If he gets one or two of the Dons,he seals his own fate. He's got 2 sons gone,a weakened Family,and a broken spirit.He's got to know that Barz or Tatt's guy will get him and maybe Tom (maybe Fredo too, but would it matter?).
The Family passes to the strongest ,and the Corleones are a memory.
He doesn't avenge Mike,his bluff is called, and the other Dons bide their time until their move is made.The Family passes to the strongest,and the Corleones are a memory.
I think with Michael dead, Vito pulls a Frank Costello,retires,and lets the chips fall as they may.
