Who's going to be in Narnia 4; the silver chair?

I just saw Narnia 3 , and I really liked it, I know that it's based on books and there's 7 books, for the people who have read them, I wanted to ask who's going to be in Narnia 4, like in the 3rd movie Susan and Peter weren't there which was kinda dissapointing since they were there for the first 2 movies and it didn't seem complete with them not there, I heard that the 4th movie is going to be about Ueisten, [or something like that],{ the cousin }and his clmate Jil. I wanted to know if any of the 4 main kids[Lucy, Edwin, Susan, and Peter] were going to be there?