I don't imagine that there is a problem, just not out yet. Also, the Panasonic HDTV likely (in reality) has a pre-standard release version of the ports. This is not uncommon as the vendors themselves sit on many of the standards boards and are part of the standard development itself. This allows for early implementation of such technologies.
Keep in mind that the port and cable remained the same.
I would think that HDMI 2.0 will be widely available soon.
Considering that from the 280X on down (except for the 260X) they are re-branded 7000 series cards I dont think they would have included HDMI 2.0 even if they had the time too. On their new cards, a month and a half from HDMI 2.0 being announced to AMD's product launch doesn't give much time.
Besides, why do you need HDMI 2.0?
HDMI can handle everything but a 4K or 1080p 120hz display, for which there are alternatives in Dual-Link DVI and Displayport that work fine.