I don't think it will be a big improvement - I think it will become Medium Nano. Which is bad, because Medium and Wordpress (etc) already own that space, and a nano version adds nothing useful.

140c is great for one-liners and linkbait, which is - apparently - the main reason people read Twitter.

If it turns into a micro-blogging stream of extended self-expression, I think a lot of people won't have time for that.