Well I think Carlo was already in bad health by Galante's peak and after Carlo died Castellano took over. I doubt Paul was the kinda guy who would have whacked Carmine only because he blew up Carlo's grave, even though they were family.. it was just business with him and he wanted a piece of Galante's very profitable heroin business, which is why he finally okayed the hit on him.

Regardless, it's just my opinion and we're talking about a what-if scenario here anyway.