Most likely? Mario Kart. Both home console and portable versions have been five years apart since their creation; there should be another one soon.
Most wanted by me? A 2D Metroid game that does NOT involve Mr. Sakimoto. So his story and cutscenes that he inflicted on Other M, Fusion and Zero Mission won't be there to get in the way of the exploration.
Or a Kirby Canvas Curse sequel. That game was the only good Kirby game in my opinion and genuinely showed off the DS's capabilities like the following two DS installments did not. True Nintendo platforming.
What isn't likely - another Zelda in the style of Ocarina/MM/WW/TP/PH/ST. Sales have been especially poor for handheld Zelda games. While I'm sure they made a profit, sales could be a lot higher if Zelda was more of an action title like Zelda I or LttP (the Zelda games I liked) versus the weird puzzle-RPG hybrid that is Ocarina etc. that slows down the pacing too much.
What I hope won't be - 3D ports of Mario and Zelda console games. Look how badly Mario 64 DS sold compared to NSMB DS.
