I'm pretty sure no game to date is 4D as that many dimensions is beyond our feeble fleshling brain's ability to comprehend.
But in all seriousness I'm going to assume what you mean is 3D movement. Sins has it, but it's so poorly implemented it's more of an exploit then anything else. It would certainly be refreshing to have meaningful three dimensional movement, but sadly I think sins isn't quite the game for it. There's already so much to manage, especially when fleets get large.
Not to mention It would throw away much of the game's tactical zone control most notably provided by static defenses and starbases. Yes you could still control areas of space, but expanding to common-use 3-D space would create a MUCH wider area to protect considering the zie of planets & gravity wells as compared to ships.
Well, I'd be thrilled if some game developer were to prove me wrong- perhaps I'm just being overly pessimistic.