Is Policy-Based Management dead? Is it scalable?
I liked it and have not seen it being removed anywhere so far.  I used PowerShell DSC since the beta and it's great but it is no replacement for PBM.  DSC is great for enforcing system states and some SQL states.  I can use it to roll out automated testing environments and ensure all the domain membership, firewalls, users, restored databases, masked data, shares, etc. are all done.  

Then PBM would be used to help out in areas that I want a report to meet compliance requirements, actually enforcing state on the fly.  DCS has a check in time where it scans, and it requires you to write custom scripts to test and apply changes if the test fails, it also requires a central server.  

I like both but for very different purposes and PBM can be very helpful if deployed as part of a greater effort.