This.
I think DLC gets a bad rep... because devs have given it a bad rep. Probably 90% of DLC is on disc, or retailer exclusive, or day one dlc. Lots of bullshit. Basically locking part of the finished game away behind a paywall. I get the feeling that many Nintendo fans believe this is how Nintendo would handle DLC with their games. This, of course, is the wrong kind of DLC, and no one wants this kind of DLC.
Nintendo is not Capcpom.
I don't believe Nintendo would pull a Cross Tekken with their DLC habits. If Smash Bros got DLC, I predict it would be similar to New Super Luigi U. Some time after the release of the initial game (probably a year or two), a "Super" version of Smash 4 is released either as $30 DLC for anyone who owns the game, or $60 for the stand alone version. Probably cheaper. It includes new characters, stages, music, balance changes, and more.
No one should be opposed to that, because it would be awesome. I don't know about you, but I don't like waiting 6 years between Smash Bros games. DLC gives Sakurai and team a way of keeping the game alive during the long wait for a new Smash Bros.
It also helps that Smash Bros might be the game that lends itself most to DLC out of any game ever made. Besides the obvious characters and stages, we could get new music, taunts, character entrances, new single player modes (additional break the target stages, additional event matches), new multiplayer modes, alternate costumes for characters... the list goes on.
I think Nintendo knows how to do properly, and I look forward to them incorporating it into Smash Bros. sakurai pls ;_;