There is still nothing that enables one to broadcast information and enable real time conversations better than twitter for companies, governments orgs or celebrities.
That twitter cannot extract value from these cash rich and price insensitive entities is a gigantic mystery.
If Twitter charges even just a little for influencers to post, lots of them will just shift more of their announcements to Facebook status updates -- a somewhat similar feature of the other social app everyone already has installed.
Despite no one platform offering exact feature+UX parity with Twitter, there are several other free platforms that are good enough for people. If Twitter makes changes that make posting on it harder, its still-organically-growing competitors could see an influx of people who will choose to abandon Twitter.