So based on what we currently know about DX12 features and hardware, it looks like this:
Confirmed fake.
GCN does not support Conservative Rasterization in any of its versions.
http://images.anandtech.com/reviews/video/dx12/fls/290X.png
http://images.anandtech.com/reviews/video/dx12/fls/285.png
http://images.anandtech.com/reviews/video/dx12/fls/7970.png
Also NVIIDA GPUs:
http://images.anandtech.com/reviews/video/dx12/fls/GTX980.png
http://images.anandtech.com/reviews/video/dx12/fls/GTX680.png
http://images.anandtech.com/reviews/video/dx12/fls/GTX750Ti.png
Beyond3D guy made this table from above screenshots.
