I don't think your stuff will become any of that, you put a lot of work into your Imports/PSA's, also even when a future hackable game one day comes that has better graphics it doesn't mean brawl hacks will fade away far from it, even the oldest games can still remain just as fun as they once were because anything these games may lack in graphics compared to the games of today they make up for in substance and brawl has substance in spades. No other game allows for custom movesets to the level that brawl has, for this reason brawl has become the precursor of what all hacked games should inspire to be like.
This is so true, just look at Super Mario 64 and Super Mario World, they're both over 15 years old, and still have hacks made for them constantly thanks to the improvements to the tools over the years, same with Ocarina of Time/Majora's Mask, GoldenEye 007/Perfect Dark and other old classics. They're extremely outdated in terms of graphics and file size, but as people constantly make hacks for them, the tools are constantly upgraded like Skelux and his branch of frauber's Mario64LevelImporter. You can now have 10,000+ faces in a custom SM64 level, original limit being 6,000-something, more music slots than before, scrolling textures which weren't available two years ago, and other edits to tools from other hackers making Super Mario 64 hacking better and better. I've only hacked SM64 for 3 years, Brawl about 2, and other the course of this time both have improved in hacking tools making it better and easier than before, and then it amazes me when I look at older videos and previews of the tools at earlier stages and see how far hacking has come. And Super Mario 64: The Missing Stars is still well known for being the first full SM64 hack ever which was made before we had all the tools that we have now. Infact frauber had to manually modify the coding to place the objects and other things that you can simply do with his level importer and Staraxxon/Vl-Tone's Toad's Tool 64 program, and then Skelux's hack Super Mario Star Road got featured in his local magazine with the headline "Super Mario 64 1.5" and it was just as complete as The Missing Stars but took it to the next level...oh yah and Skelux made Luigi a playable second player for Super Mario 64...something that Shigeru Miyamoto himself wanted in that game's development...see over fifteen years since the game's release, and a simple hacker made something that the creator of Mario wanted to be made to be real. Imagine if the community had died off and no one worked on SM64 hacks anymore, besides a huge decrease of youtube videos, there'd be an amazing hack we'd never have. The same kind of thing will most likely happen with Brawl, especially with Project M possibly making a workable clone engine, there's plenty of room for hacks involving expanding the character selection and popular movesets.
Anyways in short, Brawl hacks aren't going to die off, the community might shrink but there'll still be people who continue to work on these movesets, and as new games come out with (hopefully) new characters, hackers will strive to get them in Brawl, whether with importing the model straight from the game or custom edits to the models, or just recolor the textures, which will keep this community alive. Practically the only game that is better in hacking than Brawl is Super Mario World with it's LunarMagic where you can literally do anything, look at Brutal Mario, you've got Mega Man and Kirby bosses that behave exactly like their original selves, complete with their original sprites and sounds. You can give Mario new moves, make new maps and more. A lot of it isn't as simple as Brawl's but it's isn't as hard as manually modifying the main coding of the rom, there's coding but it's slightly easier.
I hope I sorta inspired you to not give up, or atleast to not worry about your hacks being meanless. They might become outdated, but if they do, they can still be the base of the inspiration of a better version that a future hacker makes.
If it helps any, I still look forward to your hacks, especially K Rool over Donkey Kong because I like the idea of using moves from the Country series.