It doesn't seem that themed microgames will be that common again. Not at this rate, at least.
But if there's a Game & Wario 2, she could take on a set of casino games like slot machines, roulette, and card games (like Luigi's minigames in Super Mario 64 DS).
I'd say Game and Wario almost counts as themed, in the sense that Jimmy's back to sports and the characters are doing stuff relavent to their personalities/careers? Not totally analogous I guess... If we do get a main series title for the 3DS, I can't really see how it would keep mechanics gimmicks since the 3DS can't really do much more than the DS. Maybe motion controls, but that's a bit awkward and seems like a rehash of Smooth Moves/Twisted. Actually since the Wii U and 3DS both have all the gimmicks of the last 3, I'd love to see a HD remastering like with Rhythm Heaven! Knowing WarioWare, they could even give it a tongue-in-cheek story where Wario's friends stop wanting to develop and he just reuses the old stuff while they pursue other things. I'd love to see DIY comparability too, but that might be a bit optimistic...
I think that's exactly the problem about how WarioWare seems to have run into a brick wall lately. Most of what the current systems have right now have already been done by their predecessors, and for the longest time, WarioWare seems to have been treated like a "test subject" for Nintendo to try out new hardware.