It's all but confirmed that Smash for Wii U will get the "Mario Kart 8 Deluxe" treatment. It's not far-fetched to think they'll add a couple new characters to help justify the purchase further. I'm sure there's been plenty of "Smash Bros Dream Roster" threads but it's semi relevant again so fuck it. If Nintendo/Sora could only include two new characters, who would you like to see?
Personally, I come from the perspective of a super-fan of the series and active member of the competitive scene, so I'd like to see Ice Climbers and Wolf from previous games return, just to see how they would shake up the current meta.