Surely the future will be H.265 content which will have better quality for the same bandwidth. And it's unlikely that people are going to be demanding a higher output resolution than 1080p from their mobile device for anytime soon.
I could imagine people want to play 4k movies from their mobile device on their TV, but you wouldn't install a 4k screen as the display on the mobile device.
Edit: Yes, computer is inaccurate. I wanted to get the idea across that we are talking about connectors (DVI, HDMI) that you would normally use to hook up a computer or laptop to a TV or LCD. They have only recently appeared on mobile devices, but serve the same purpose here: video (and audio, for HDMI) out.
Huh? Its the plug on the bottom of a phone (and ipads now i guess). Lightning isn't on any computers.
b) Why is there a second pass compression/decompression stage ? Isn't iOS outputting the compressed H.264 stream and the adapter decoding it i.e. one stage ?
c) Given that Retina displays by definition are the best resolution we will need and it is far less than 4K it is questionable whether there will be a use for 4K on mobile devices. Other than using your iOS device as a media player for your TV (very small use case).