The new AMD architecture doesn't seem to offer support for HDMI 2.0, but instead still uses HDMI 1.4a.
This means with Fury GPU based products, like the new project Quantum for example which really is a small form factor PC, you can't fully use it on an Ultra HD TV.
HDMI offer bandwidth support for 60hz, on 1.4a it'll drop back to a measly 30 Hz. A big miss if you ask me, HDMI 2.0 is the answer for products in the living room. Especially Nano and Project Quantum in mind, this might not have been the smartest move from the engineering team within AMD.
It's a bit of a thing for 4K gaming in the living room I'd say.
This question was answered by AMD Matt from our forums:
Q: Does the AMD Radeon R9 Fury X GPU have HDMI 2.0?
A: No. AMD recommends and uses DisplayPort 1.2a for 4K60 content.