Can the developer still update their app, or is it stuck in update limbo?
You can request faster reviews for critical security bugs, but as far as I know, if you're rejected for guideline violations, you're stuck until you alleviate those violations.
This is actually another problem with the whole review process: There often isn't a clear guideline/way to tell. You can submit an update that goes through quickly, or wait for months, without knowing why. Valve, the company that runs Steam, also had horror stories about this. They published the Steam Chat app (not a store) and had to wait for months for approval, apparently without being able to talk to anyone at Apple.