Regarding Planescape - my impression is that ever since the collapse of 2E, D&D has been much more limited in how many different official settings it will support. The business logic is that different settings fragment the customer base and make it harder to have network effects, which is D&D's strength. From what I read, Planescape hasn't been officially supported in any of 3E, 3.5E, or 4E.
On the other hand, there is an excellent Masque of Red Death official release in DM's Guild. So they are supporting some settings with minor releases. I did find a 61-page 5th edition Guide to Planescape that looked semi-official, but it seems like it is not being published - possibly an aborted attempt to get it published under the third-party license.