I think there's a chance of Slack winning this use case when they add one feature: threaded conversations / topics. Zulip (https://zulip.org https://zulip.org)

I think there's a chance of Slack winning this use case when they add one feature: threaded conversations / topics. Zulip (https://zulip.org https://zulip.org), Dropbox's Slack clone, supports threaded convos out of the box quite nicely.