If that happened I'd be tempted to ditch tumblr entirely honestly. I don't like how tumblr doesn't let you do that, I'd like to reblog stuff and not have it appear on my main gallery, just on other people's feeds.
I've already been through twitter's bullshit of trying to cultivate a non spammy media tab (aka trying to not post many images except art so people can see my art if they click there), I've seen too many artists on twitter who could really benefit from a gallery, their media tab was just full of reaction images, which are fine but again it makes it harder to see their art.
I'm not making cohost my "main site" if/when twitter dies because that's not the goal of this site, but if they had a feature like that for artists? It'd be neat.