I doubt there will ever be a 4k x 2k disc standard. Hollywood is idiotic. On the one hand, they really want to sell discs. On the other hand, they want to do everything they can to stop you from having clear ownership of a physical format.
Maybe there'll be a Really Really Blu Ray around decade's end, but I'm not holding my breath. It'll likely be delivered over the net.
There is no difference in HDMI cables. If you can see the picture without visible dropouts or sparklies, the cable is working at 100%. No other cable will display a better version of that picture. You're simply wrong if you think there is a better digital cable than one that is already working.