Let's be honest. Clients using the OS's task scheduler are never going to go away. We can hope they're needed less often as more services integrate ACME natively. But there will always be scenarios where a simple client using a simple scheduler are all that is needed or wanted. I'd suspect a decent chunk of the services with native ACME integration will also just be using simple timers or schedulers via their language's class library as well.
All ARI is going to do for scheduled clients that support it is change the recommended wake-up window to be more often.