Twitter's traffic will ebb and flow. But as with all social engagements, metrics don't tell the story that matters. Success for a platform will won't be in short term spikes, but in cultivating sustainable relationships on the platform, a steady place in the user lifestream.
I don't know that Twitter will be where we socialize in 2020. But I do know that this user behavior is not going away. Ignore the buzz. Do what you need to do, do what you should be doing and lead your own path.