This has been announced, as a partnership between Slack and Atlassian. HipChat and Stride users will be migrated to Slack. End of this story.
Most of the too many Team Chat actors will disappear thanks to darwinism applied to IT ecosystem. With Slack consolidating its leadership on the market, the natural selection will accelerate.
Most of the Team Chat players joined the bandwagon, because it is the first generation of Instant Messaging that monetises. Most of the Team Chat players only cloned a subset of what makes Slack pretty good, none have really innovated on top of it.
So, we see one more massive centralisation of users, under a proprietary silo, that is not even reliable…