Sad to say,this has been on the cards for some time. There was never any doubt about sequels to Spider-man or Batman Begins, for example. Superman seemed to be followed by the pattern that also emerged after Ang Lee's Hulk. Rumour, rumour, less and less sign of movement, cast and crew moving onto other things ...
With the reboot proving successful for the Batman series, the Bond movies, though less so for Hulk, it's perhaps inevitable that WB would consider this approach for Superman. After all, SR, much as I like it, was an underperformer financially (people were expecting Spider-man like box office returns) and divided fans down the middle. You can never please everyone, but the movie never received the love that BB or Spider-man did. I think picking up where it left off (with a 10 year old Jason etc) might be a risky proposition. Ignoring that sort of baggage and delivering a more fun movie (like the Incredible Hulk) seems a lot safer.
Count me in on the Bring Back Routh camp though. I thought he was the perfect successor to Reeve and he can only be better, now that he's more grown up and mature looking. I don't care if the next movie is a reboot and he's the only actor from SR in it - if the much less indispensable Judi Dench can be in the Pierce Brosnan Bond movies and Casino Royale, then why can't Routh save WB a multi zillion dollar search for a new man to wear the cape?