I'm all for DLC as long as it's worth buying if they're going to put out DLC make it worth my money. Make them packages new character, new stage, new music, possibly new items, new statues, new stickers (assuming they return) and etc... So say they decided to do a Travis Touchdown DLC just as an example So you would get Travis Touchdown, a stage from No More Hero's, some items from it, music, hell maybe even some event matches based on NMH. Would that be worth $5-$7 from me? Ya sure why not? Also depending on how much effort they wanted to put into the DLC they could put out new side stories or something like that (though I doubt that will actually happen) and charge more for that. Add 3-6 more hours of gameplay to the game I'd pay $10-$20 for that. Personally I'm all for updates and DLC because they can be used to fix potential problems (such as balance issues) with the game as well as add new content thus extending the replayability of the game.
I mentioned this in another thread about DLC but, DLC could also be used as a great way to advertise for new games. Example, there's a new Zelda coming out well there could be free DLC where Link, Zelda, Gannondorf get new costumes reflecting the look and style of the new gaming coming out. And maybe there's a new statue that you can unlock that will give you a tease of information about the upcoming game. That's a great use of DLC and a good way to give the fans of Nintendo a little extra nod.
The final thing that DLC is good for is user shared content. The idea of sharing stages can come back and be improved upon maybe rather than getting just one random stage a day you could look through all the stages made by users, much like little big planet, so people can browse through the user made stages and pick the one's they want to download. This would add a swath of new maps available to players of the game to have access to and enjoy. I think this would be more difficult to do but still a great idea I think user generated music would also be an awesome idea there are lots of talented people out there who make great video game music remixes, spend a day or two checking out ocremixes and you'll see, that would add a nice option for lots of new user generated music which would be a lot of fun in my opinion.
Some of this stuff is a little ambiguous and would probably harder to implement than others but still I think they're some decent ideas.