I have no idea if there will be a 3DS Metroid coming out soon, but something like that could have a lot of potential, I think.
I’d want a 3DS game to be a side-scroller, though it could probably have a 2.5D sort of style similar to how Sonic 4 looks. Though honestly, as long as the game handles like Fusion, ZM or Super, I doubt I’ll be too picky as to how it looks. I also think that in a 2D game the touch screen could be useful by showing you your map or inventory at all times.
I wouldn’t want a fully 3D game like Hunters. I’m not saying that I didn’t like Hunters (I thought it was enjoyable enough), but it’s just been way too long since we’ve had any 2D games. Those were my favourite ones from the series (though I absolutely love the Prime series), and it’s been years since we’ve had any Metroid sidescrollers.
And one last thing that I’d want from a 3DS game (regardless of it being 2D or 3D), is that it chronologically takes place after Fusion.
The theme that I use is called “Lookbook”, which is free to use.