The other market is a bit more saturated, with Microsoft and a few others piling on top too. Whereas the Gaming market was completely lacking. There were a few clients which focused much more on voice (mumble, vent, ts), but nothing quite like Discord. Free and one-button to make a new server.
The only other contender I can think of is Raidcall, but that was a joke... Now there's Curse but they came too late to the market and were DoA, except the people they forced to use it by paying thousands.
Are companies a market you're serious about? There is so much focus on gaming, it's hard to be sure. I mentioned to support recently one of our prime issues as a company is being limited to a single owner per server.
PS: Are you the same Stanislav Vishnevskiy I'm thinking about? I remember working on Guildwork with you!
Add me on Discord if you wanna chat Stanislav#7943
Definitely not paying users / valuation currently. Slack is pretty massive there.
Edit: Appears it's still missing from some servers!
I've noticed that Slack performs a lot worse than HipChat.
It's really too bad that they didn't take advantage of it, since they were actually scalable compared to their competitors and had good voice chat. Slack has started becoming more scalable recently, so I don't know how much the opportunity is still there.