Microsoft are now looking to compete with Slack.
In the article it mentions how they fail to see what the future of Yammer would be and they struggle to see where it fits in. In my eyes they have completely different capabilities.
Yammer is about networking, relationship and community building. It enables discovery, innovation, crowdsourcing and engagement that potentially involves hundreds and thousands of colleagues.
You would struggle to do that with Slack or Skype teams. The key word here is teams. Skype Teams would work well with defined, identifiable colleagues – in essence building around existing hierarchy and structures.
With Yammer you discover and network with people and groups you never knew existed before, creating new ways of working through the diversity that can be attracted through discover.