Actually, UnderBoss but you seem to be wrong...

On the comentary of GF2, Coppala says that the actor playing Clemenza, said that he would only be in the film if his assistand wrote all of his lines. Needless to say, FFC disagreed but it wasn't until just before shooting, he realized that there would be no Clemenza. So FFCm along with Puzo's hepl changed a few lines and made Clemenza into Pentangalli.

So, no, no one expected Clemenza would not be playing in GF2. And the Sicilian, I believe does have a Micheal and Vito Corleone in it, but no Clemenza.