Yes, Brawl has no future as a competitive game. As long as people still enjoy and play it, it is not "dead" in a technical sense. But in terms of competitive play, Brawl will eventually give way to Melee, which is in its platinum era now, and Sm4sh, which is one the rise.
The fundamental reason why doesn't have to do with the tired arguments people always trot out against Brawl: slower playstyle, the idiotic tripping mechanic, Meta Knight being OP, so many characters being complete garbage tier, lack of wavedashing...etc. The major, fundamental reason has to do with the intention and mindset going into the game's development.
Brawl was Sakurai's middle finger to the competitive community. Nintendo specifically developed Brawl for the casual community, and as a result, gave us a great party game, but a VERY subpar Smash game. Brawl is unquestionably the worst installment in the Smash franchise, but is still a very good game overall. I've enjoyed great memories with it. However, it was not designed to be a competitive game played on a professional level. Melee turned out that way really by accident - and Brawl was Nintendo's way of flipping off the competitive community in favor of catering to the casuals.
We should be grateful for all Brawl has given us on a personal level and that Nintendo is actually (at least somewhat) considering the competitive community now via Smash 4 and its For Glory mode. But Brawl has absolutely no future or hope of a competitive renaissance, except maybe Project M. But we saw where THAT went...
Maybe me and all the other naysayers are completely off base, but from what I have observed in my meager little experience, Sm4sh and Melee have stormed in, and most people have deserted Brawl and never looked back.