and that is exactly when slack will die and something else will come in to take its place. an endless cycle
I saw Salesforce buy/eat Demandware. It's called Salesforce Commerce Cloud now. I bet something similar will happen to Slack.
I saw it too, and IMO the ecosystem is better than ever now. It took a few years of stagnation for SF to really dig their hooks in, but everything is nice and integrated now.