Who is tracking the Slack IPO? Slack Technologies Inc. was expected to be valued by investors at $16 billion to $17 billion when it listed its shares publicly last week. More than 600K organizations worldwide use Slack. When Slack went public it traded for $38.50 well above its reference price of $26 and by mid afternoon on June 20th closed at $41. What are you predictions for Slack - think it will continue to be successful?