Native 5k resolution in Windows 10 on retina iMac
It is as of TODAY - well, for me at least. I have been stuck to 4K for as long as everyone else had, but early this morning the Apple Update utility asked to install a new version of Bootcamp drivers. I let it do its thing and... voila. Native 5K res on the next boot!

Don't know if it had anything to do with Microsoft's own November Update for Windows 10, but I am truly happy it did happen at last (I had given up hope to be honest). Just make sure that you do NOT let a later version of AMD's drivers overwrite these, as it's likely to return the resolution to 4K. I know I won't.