This is a hard one to call, much depends on individual issues. I have heard that the elements of Godfather One are in need of a full restoration and the team that did Vertigo, Spartacus, etc. wants to do it. I note that the review of the new set on dvdfile.com noticed that GF One looked somewhat below 2& 3. It could be years before a restoration is done, if at all.
In my case I have the LD set so I'm going to wait. I'm still waiting for an enhanced Vertigo. Waiting is difficult but I resisted on Die Hard, Last of The Mohicans, etc., so sometimes it pays off. But, I sure will rent the Godfather set and watch it in the meantime. Who knows, maybe it will be good enough where I don't have to wait.