> Our priority is to provide a secure and high-quality experience across all platforms, and so the time has come to close the gateways.

The IRC gateway was the only way I was interacting with Slack. If it's gone, I'll just stop using Slack. That's ok, but is not exactly providing me a "high-quality" experience. (Meanwhile: IRC clients are capable of connecting to servers with TLS and authenticating certificates in the same manner as web browsers. So I'm not sure about the "secure" criticism either.)

Is there an API that will continue to be available going forward that 3rd party software can interact with?

weechat has a slack api based plugin https://github.com/wee-slack/wee-slack