Not concerned. I didn't have Twitter before, and I don't plan to get one now regardless of who owns it. The social media I already have, is enough for my purposes. And I don't really engage with people in the way that Twitter is made for. It was never something I needed, so I never got into it. Other platforms work better for me.
I guess I'm against the idea of billionaires in general, because I feel like no one person, or even a small group of people, should have that much power to determine the entire direction of humanity, for everyone else. I think it's causing the problems we have today, because they have us stuck playing their game long after we should have evolved to something else, long after this game doesn't work for most people anymore because technology is too efficient now (and the laws have become lopsided now to favor the upper class instead of being balanced, resulting in the destruction of the social safety net), but they don't want to do that, they want to keep playing this game because they're winning at it.
For the record I don't like communist dictators, or dictators of any other ideology, either. Billionaires, dictators, whoever, no one person or small group of people should have that much power over everyone else and to set the course for all of humanity, cause then we're stuck doing their vision, which winds up favoring them over everyone else. Instead I think we should strive for a world where everyone is free to follow their own vision, as long as that vision isn't harmful.
But anyway, this stuff doesn't only apply to Twitter. As far as Twitter goes people will either continue to use it or not, and if not, something else will take its place. No skin off my nose, either way.