Knowing that the development team won't be spending as much time on a contrived and tedious adventure mode puts my mind at ease. Smash Bros. never revolved around single player modes, so I've never understood the need to flesh out features like the Stadium, Adventure, Events, and so forth. Personally, I feel they should simply leave the single player modes to Classic (homage to the original view that a child was playing with his Nintendo toys), All-Stars (being the point of the entire game: a collection of Nintendo's stars), and an individualized yet minimal story plot for each character (exactly what they're going for this time around). Break the Targets and Board the Platforms never really concerned me; if they do make a comeback, however, then they better not be half-assed like they were in Brawl.
What I really want to see them focus on is multi-player. Let us mix and mash more game modes--we're already able to combine stock and time, so why can't we throw stamina in there as well? Offer something new and exciting, like tag teams. Expand on the mechanics of items, perhaps allowing us to allow static spawn points and time intervals for appearance. Establish a more worthwhile tournament system, adding in a proper picks and bans feature that gives the mode actual use. Spend less time on gimmicks like "flower mode" and "fixed camera angle mode". Pour all your attention and resources into the angle of the game that matters most. This is something Brawl missed out on.