Hi everyone! My name is Hallie and I’m a Program Manager on our CXM Team. I wanted to share an update on this feature request. 
While the ability to delete tasks via workflows isn’t currently planned, the ability to mark tasks as complete is available with task workflows. Additionally, Task Assistant is an example of an integration that supports deleting tasks via workflows - you can read more about what it can do on its listing page. Because there is an alternative option for automating the completion of tasks, we will mark this as ‘Alternative Solution’. I hope this helps!