No way in hell. GFRturns and GFRvenge BOTH have NUMEROUS major breaks with canon as already established in the movies, to make any further GF movies using Returns or Revenge as a basis would, in effect, throw III and part of II out of canon.

Returns and Revenge have to be simply considered as "Elseworlds" or "Imaginary Stories" loosely based on the Corleone characters, and only peripherally involving them in the storyline.

Now, if they want to make a "Nick Gerace" movie -- focusing almost completely on him -- and maybe mention in passing that he knows, or knows of, the Corleone Family, that might work.

But no established character from the Godfather movies should appear onscreen in a Nick Gerace movie.