Harmy had made a point about 4k at home, saying that at the size of home televisions the extra resolution doesn't help all that much and that we'd be better off focusing on 1080p with less compression. For whatever it's worth, Apple's definition of a "retina display" bears this out. You can play with numbers here:

The general notion being that at most TV sizes and a typical viewing distance the pixels are smaller than your eye's ability to pick them out already. A 1080p TV viewed from seven feet away qualifies as a retina display (again using Apple's definition which is mostly marketing but does make some degree of sense).

I'm not too sure we'll see TVs get much larger than 50-something inches for a while. Bigger than that and they become very imposing pieces of furniture. Maybe as panels get thin enough it'll be more feasible to cover large portions of walls with them, but that still rules out diagonal placements and you start talking about something much more like home theaters.