First we heard that Brendan Fraser and Rachel Weisz would be asked back for "The Mummy 3," but then came word that the sequel would focus on the exploits of their now-grown son. Well, it looks like both are actually the case.
In an interview between iFMagazine and screenwriter Alfred Gough, the following details were revealed:
1. Not set in Egypt.
2. Doesn’t deal with Im-Ho-Tep at all.
3. "The plan is to bring Brendan Fraser and Rachel Weisz back."
4. Along with his writing partner Miles Millar, Gough worked on the "Mummy 3" story alongside series creator Stephen Sommers.
5. Yes, the movie is still to be directed by Rob Cohen.
Sources: IGN Movies, iFMagazine.com