Just don't buy a 4K TV for the sake of your Apple TV because with the quality of built-in apps on today's quality 4K panels you'll find you barely use your Apple TV at all.
This happened to me a year ago when I moved on from my 8 year old 1080p panel and went up a screen size and got a 4K panel. The built-in apps on the TV like Netflix, YouTube, Prime, HBO, and the rest have the same UI as the Apple TV versions and most offer better compatibility for the tech that is important in the 4K world like 4K content, HDR, UHD, and others that aren't yet available in the Apple versions.
These days, my Apple TV is my music player and the gadget that lets me airplay my home videos to the big screen, nothing more. It's a shame, but smart 4K TV's really do render standalone streamers obsolete.