Let's face it - there's almost 100% chance that the film will not go ahead if there are no new stars.
So I think the big question regarding GB3 now is: Would we rather see…
1) A movie with Dan Aykroyd, Bill Murray, Harold Ramis, Sigourney Weaver, Rick Moranis, Ernie Hudson, and Ivan Reitman; made in perfect tradition of the past two films, with a great script and plot; and just being generally what we want it to be - but having it fall flat financially and become unliked with many of the younger members of our society? If this is what happens, those who are not “ghostheads” may be turned off by the new film and thus with the entire franchise, which then causes our GB community to grow smaller. So in this case, the end result would be a great GB film which satisfies us, but does little to promote GB-awareness amongst non-ghostheads.
Do we want this, or…
2) A movie with mostly new, popular actors, with small cameos by the original cast; somewhat in the style of EGB; generally a film which fails to follow in GB tradition. This doesn't really sound that great to us, but it has more box-office potential than the above idea, and this could result in new GB fans. Now, chances are, if these new fans enjoy GB3, they'll definetly take a look at its predecessors, grow to love the first two movies, and become “ghostheads”. This in turn helps the GB community to grow.
So what would you rather have?