It got downvoted because not only didn't Apple shut down the app, they chose to massively boost its user base by making it free. Not a policy very consistent with discouraging its approach.

So you're confident that they won't replace the URL handler behavior with something else?

I've got no idea. Conceivably they could come out with a new approach and transition Workflow to it by having it support both mechanisms. That might be easier to do and be less disruptive to users if the app is in-house. But even if they do introduce a new mechanism, existing apps would still have to adopt it which would take years.

So absolutely Apple could introduce a new mechanism, but their buying and encouraging adoption of Workflow is a strong indication to me that they have no intention of deprecating the URL mechanism any time soon.

I agree here. If they do have an idea for improved inter-app automation or "dialogue", this would be a great example case and implementation of it. Plus this team's knowledge in this field could help guide what's needed, and also help out with Siri stuff to do on-the-fly "workflows".