A recent Twitter post may have given some hints about Smash Bros. 3DS. It would seem that it is listed as a "Coming Soon" title, but it's the location that makes this interesting.
Every week, Nintendo updates their eShop and separates products into categories. The relevance of this is linked to the fact that Super Smash Bros. is located within the "Wario" category.
Click the jump to see what I mean.