No, if we were going to create a new official Ubuntu communication channel it should be on Rocket Chat since Rocket is completely free and open-source and thus Ubuntu would have full control of its data on there and be able to file bugs and contribute to development as it wished. Moving to Rocket Chat is effectively being rejected on the grounds that it fragments the community and Slack would do the same.
Sure, if you want to make an unofficial Ubuntu Slack to see what happens then go ahead, but it shouldn’t be official and I don’t think it would be wise. Best to stick to the official channels and centralize information there, despite the inaccessibility and lack of persistence of IRC (at least we have this hub, forums, Reddit, Ask Ubuntu, Launchpad…)