What's interesting is what value Twitter gives and what could a new platform target? For me, there's a slice of Twitter users that provide information, entertainment, and context that I can't get elsewhere. This could be something from a mid-level analyst re: market volatility or a college professor at a small Canadian university on Chinese politics. These people aren't consistent enough or polished enough to have established means of amplifying their opinions (a blog, newsletter, podcast, etc.) though they have so much domain expertise. Where do you find them? On Twitter. The low friction posting encourages them to share.
If I could get rid of the celebrities, the thought leaders, the self marketers, the low content hate, and the bots, and only be left with the above in a moderated environment I'd welcome this global town square.