I don't think it's likely that there will be a "Twitter alternative" or that people would flock to another Twitter, but I think it's more likely that the reason you might use twitter becomes less important as your focus shifts elsewhere, and then you just have less of an interest in it. I can't think of a clone/off shoot of a popular service that actually stayed successful or became more successful, without some hook/features of the new one (Reddit is probably the only one, but even then I think Reddit became way bigger than Digg because of unique features to Reddit).
I quit Facebook back in ~2015 or so, I had quit earlier, came back, used it for a while, but then finally quit for good. And it's not because I found a Facebook alternative, but because Facebook stopped offering value to me, I thought it had a negative influence in my day to day life, and decided I didn't need to be on it and I'd be happier without it. So far that's been 100% true.
The only social media service that I really *enjoy* using is pretty much TikTok, like I actually enjoy using TikTok... I get really funny videos, interesting videos, and the stuff I don't like I can pretty quickly skip. But even just 2 or 3 years ago the thought of me using a Vine-like service would have seemed really unlikely to me... "why would I want to watch teen dance videos or people singing, I hate that shit?" Little did I know that TikTok is full of videos of weird dumb life hacks, animals doing dumb shit, basketball videos, dumb videogame clips, cooking guides, etc, and that I just love vegging out to that content.
There was a time that I used to similarly really enjoy using Twittter, probably like 10 years ago, "watching something with the world" around sports or TV, I really loved that, and it felt really new... "Live Tweeting" something was just such a cool thing and it sounds so dumb to say that now but it was for me, but as twitter juiced the feed to be more algorithmic, less timely, even though I use the reverse chronological setting, that community around shared watch-alongs is mostly gone. I think also I watch/interact with less live content too as streaming has become my de facto way to watch video.