We'll probably be seeing the last high-end plasmas ever in about 5 years. They will be marginally better than this year's TVs. Of course, LCDs aren't much improving either. The LCD of 2017 will be (a) not much better than 2012's model and (b) not much different from 2022's.
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.