Exactly, it's no good saying that 4k will be more popular and common in 6 years. That very well might be true, but the PS4 is being sold at the most in two years time. They don't have the luxury to be able to afford to put tech in powerful enough for 4k and make the console cost $600 so that in 4 years time more people can benefit it, they have to work to the now and right now they can't afford to put 4k gaming capable hardware in the PS4 when it will benefit a tiny minority to begin with.
I mean how do you even sell that? For the PS3 the price was ridiculous but they at least had pretty good reasoning, people already had HDTVs, HDTV was a broadcast format when it launched and so putting out a console with a Blu-Ray drive was expensive, but something a large number would make use of right away.
4k however, wouldn't. Let's just imagine here that the PS4 launches in late 2013, costs $600+ and they have to explain why it costs that much? Are the masses going to be impressed when they say it's because in the future, when 4K TVs are much more affordable, they'll be able to game in 4k?
People want a benefit NOW when they pay for new hardware, not what they might be able to do with it theee or four years down the line.