I am pretty sure that Mr. Wizard said that in order for Melee to come back, Nintendo has to want it back. I don't really see how this game will die anytime soon. I know that in America it won't anyways, because we have at least a few areas that have a lot of people that play. As far as the national tournaments costing a lot, we may just decrease the number of nationals. It would be pretty cool if we could expand internationally though because a lot of Europe doesn't seem to have big scenes (though I could be wrong). As long as there are people to play against and a metagame to advance Melee should be fine, because honestly, I think that, with the exception of Fox and MAYBE Falco, low-tiers have a LOT of development to go before reaching their potential. Mewtwo, Yoshi, Ness, Pika, and Link seem to be having huge pushes by SOMEBODY. Taj, Vman/Amsa, Mofo, Axe, and Mofat are the ones I can think of for the Low tiers and I guess Pika is mid-tier. Anyways, I think that players like Ken, Mango, Armada, Axe, Shroomed, Mofo, Taj, Vman, and Hax, to name a few, have shown us that these characters are not done evolving. Plus this game gets so much hype from viewers. Its fast, technical, and there are many intricacies to it that many fighters do not have to deal with, like stages.
tl;dr: The characters can be pushed much further, and the fanbase has room to grow now that the FGC is showing some respect.