I would wait for further confirmation before assuming that the next Superman film is going to be a 100% reboot. "Reintroduce Superman" could mean a complete reboot with a new cast or it could be a sequel with the same cast that goes in a very different direction to Superman Returns
. The former is more likely given Robinov's words, but I don't think it's completely clear yet.
As for a dark Superman film, I think a relatively dark Superman film could work just fine as long as you get the right mix of action and the right characterization. The Darkseid arc in Superman: The Animated Series
was dark, particularly the climatic confrontation between Superman and Darkseid in "Legacy", and it was incredibly good. If they did something like that in a live action feature I think it would be very successful.
As for Robinov's statement about DC films in general, note that he said he wanted them to be "dark to the extent that the characters allow it". So they're not all going to be as dark as TDK