More than six million people use Slack every day as a hub and platform for communicating and sharing information with their coworkers. The San Francisco–based company also just raised $250 million more in funding, in a round that puts its value at a lofty $5.1 billion. But new competitors - among them Microsoft Teams, Atlassian Stride, Google Hangouts Chat, and Workplace by Facebook - are pushing into the workplace-collaboration market, challenging Slack’s dominance and, in some cases, specifically marketing themselves as more productive options. Here's how Slack wants to stay relevant in the years to come. Get the full story at MIT Technology Review