Why else would you do a reboot if you are not going to recast the characters. There was no real need to recast the Incredible Hulk but they did, and the characters fit more than these do.
I think we were lucky in the case of The Incredible Hulk
. As for recasting the next Superman
film, my view is "be careful what you wish for." Remember some of the names that were tossed around before Singer found Routh.
Regarding the problem of Superman's son, I think the new writers should work on it before the studio takes the drastic step of throwing Singer's cast over the side.