My guess is a wait and see how popular Netflix 4K content is.
I don't think we need to wait for 4K streaming to show online.
Isn't the question answered by looking at the slow takeup of Bluray compared with the ongoing popularity of DVD, and their relative prices? People don't mind the higher quality (though plenty can't tell the difference or sit too far away to benefit), but they don't want to pay more for it, and certainly don't want to pay *again*!
It took over a decade to go widescreen, and a similar time to go HD. Bluray has been around, what, 7-8 years now? I saw a recent projection that Bluray discs will go from 17% of the market now to 35% in 5 years. One-third bluray, 13 years after introduction?
If people don't already feel the need for HD content that is sitting on supermarket shelves, and matches the HD screen that many have, what real hope is there for 4K content in the next decade?