Are you getting a new iPhone? If so 4K recording will be in your pocket and always with you as soon as you pick up that phone... not 5 years from now. Stores already seem to have more 4K sets for sale than 1080p sets (go look) and prices are not the "thousands more" some of us keep slinging around.
My prediction is Apple will finally embrace 4K in an

TV5 about 0-6 months after the new iPhone's camera goes into iPads (so that's probably 12-18 months from now... not 5 years). That's what happened with 1080p: iPhone 1080p recording first, then iPad, then new 1080p

TV.
And TVs are usually about 10-year products. People replacing TVs "once or twice" over just 5 years must have a lot of violence at their homes (damaging the sets), live in a high-crime area (they get stolen) or have money to burn such that they need every latest & greatest update each model year (you know, like Apple people are with Apple products).
Content providers will deliver 4K as soon as this this holiday season on new 4K Blu Ray players:
http://www.cnet.com/news/4k-blu-ray-discs-arriving-in-2015-to-fight-streaming-media/ Some sources like Netflix, Amazon and YouTube already deliver some 4K via streaming. And the army of Apple iPhone buyers are about to shoot a ton of YouTube videos in 4K with their new iPhones. Surprising me, there's even real testing to make it available over the air (something I didn't expect for many more years):
http://4k.com/news/lg-zenith-others-testing-simplified-over-the-air-4k-tv-broadcasting-8153/
My (adjustment to your) prediction: in 5 years, 8K will already be obviously rising and 4K will be where 1080p is now. And 1080p sets for sale at stores will probably have as abundant a selection as the 720p sets in stores now.