Dark Link should most definitely make an appearance in the next Zelda game...no, the next Zelda games. Both Wii U and 3DS, in my opinion. We haven't seen the little bugger in a "big" release since Twilight Princess, and even then, he was restricted to a (scary but awesome) cutscene, we didn't actually FIGHT him. Again, the cutscene was scary yet awesome, but his absence wasn't justified in that game.
His absence in Skyward Sword wasn't justified in my opinion - rather than the second Ghirahim battle I'm sure a Dark Link fight would've sufficed; Ghirahim II is far too similar to Ghirahim I for me to really distinguish between the two. Sometime within SS I'm sure Dark Link, Shadow Link, Evil Link whatever you want to call him could've made a grand reappearance that 1-UPs the Ocarina of Time appearance.
The next game, I want to see this Dark Link come in full blast. Whether it is that awesome 1 on 1 sword duel, or be it that he takes to fighting us with a massive bunch of clones (Let us see Link struggle with his inner darkness, eh?), just make him FIGHT us!