People are forgetting that Star Trek was received well by fans and critics, and a sequel was a certainty after the film was released, while with SR, critics did like it (for some reason I have yet to understand) and it made a lot of money, but the overall public sentiment about the film was lukewarm. Hence the reboot.
It might be better to compare Star Trek to Batman Begins. Both of those films raked in good money and left fans and the general audience craving more. Sequels were a cetainty shortly after the first films were released. And we all know how the sequel to Batman Begins did at the box office. So while Star Trek might not have been a huge megablockbuster, there's no reason to assume that its sequel won't be. I'm sure it won't pull in TDK numbers, but it will most likely trump the numbers that the first film made.
With that in mind, if Man of Steel goes head-to-head with Star Trek 2, there's a good chance it will lose. Even if it doesn't, the two films will hurt each other's numbers. So if studios are smart, they'll leave a two week gap at the minimum.