So I'm not really a Smasher to any extent but I have been a gamer for many years. I played Halo ever since the beginning and the transition from Melee to Brawl is sort of similar to the transition between Halo 1 and Halo 2. You guys have to understand, though you may think that you have the game fully figured out, you really don't. There were things that you were still figuring out in Melee and Halo 1 was the same way.. Halo 1 was a little past his prime but still great and that's where Melee was. Melee was a great game with great glitches that MADE the game... and eventually, just like Halo 2, Brawl will find it's glitches that will MAKE the game and Brawl will become a great game...
through that transition time that could take years, unfortunately, there will be pro Smashers who will stop playing and it happens...
Brawl will have it's peak, whether it is going to be as great as Melee's is debatable beyond belief and is just going to waste everyone's time doing so.
I came from the Halo community as well and while there is some merit to the comparison, I don't think Brawl will find anything to save itself because the changes to the engine are too significant.
Changes from Halo CE to Halo 2 were mostly a series of minor changes that cumulatively made for a weaker game. For instance, larger hit boxes for online play, instant-explosion grenades, easier melees, more auto-aim, more reticule magnetism, less balanced maps, broken weapons (plasma pistol...). It was still very recognizably Halo and the game felt more or less the same, the largest MAJOR changes being the decreased viewing angle from 90 to 70 degrees, the decreased run speed, and the introduction of a hit-scan based projectile system. But someone good at Halo CE could pick up Halo 2 with no problem and in fact might not even notice some of these changes without really looking for them.
On the other hand, Brawl is an entirely differen beast from Melee. They don't feel similar at all. The core mechanics of Melee were abandoned and the new engine is completely different.
Moreover, the naive notion that glitch discovery is inevitable is not true just because it happened with SOME other games. When developers make a very conscious effort to dumb down gameplay like Nintendo did with Brawl, and when thousands of people have been deliberately searching for these glitches, knowing the kinds of things to look for, and still haven't found anything, this naive optimism becomes unwarranted.
The physics engine in the Halo games is much more complicated than Smash. There are so many possible weaponglitches, and they can be very obscure. In Halo 2 the doubleshot, for instance, is a very obscure technique that took a long time to discover because there's no reason to expect the battle rifle to perform that way. The exploits in Smash, however, are fundamental consequences of the physics engine. Wavedashing is just airdodging at an angle such that the game conserves momentum. I couldn't even begin to describe how the doubleshot works. You press R, rapidly press R again, while holding hit X. The timing is difficult. Why does it work this way? I have no idea. It's undoubtedly an actual glitch.
There were very few true glitches throughout the Smash series, I think, because the physics engines are simpler than in FPS. You don't have the complex terrains to map, just 2-D stages. You don't have to design ballistics systems for all these different guns. There are just way fewer things that can go wrong.
I don't think anything significant will come up because Nintendo tried to very hard to avoid players gaining any kind of advantage, much like Bungie did with Halo 3. Halo CE was good by accident, Halo 2 was playable by even bigger accident, but as far as I know Halo 3 is complete garbage. At some point a developer wises up to these accidents.