I doubt that Rogue Leader is going to be 5 discrete channels with full bandwidth that DD is capable of providing.
Well, yes, that's just about what DPLII does. Five, full-bandwidth channels with separation approaching that for a discrete system. I'm guessing that anyone who is down on Rogue Leader using DPLII has never actually heard DPLII in action.
For comparison, Rogue Squadron on the N64 in DPL is nice. Using DPLII, however, the sound is significantly more directional, and can be used to track enemies fairly well. And this is from a stereo signal, not tweaked for DPLII, on prior-gen hardware. I fully expect Rogue Leader, using DPLII, to provide five-channel, directional sound, nearly the same as you'd get using DD 5.1 on the other systems.
The real problem, I think, is that DPLII is new enoough that not many people will be able to take advantage of it.
Is DD better for directional sound? Yes. But DPLII is very capable, and I think will do amazing things with video games.