Looking over Gravano's testimony provided in the Gotti Tapes book, he says at one point Gaggi came to Gravano worried that Castellano was going to kill him. Gravano told him not worry because he knew Castellano was going to be killed himself soon. So I don't think he could be counted as a Castellano loyalist at the time of the hit.

I'm not sure if there were any real loyalists to Castellano after the hit. I know there was a "Castellano faction", but it seems they all eventually went along with Gotti when they realized they weren't in trouble with him.