I had a couple Apple TV3's for many years but replaced them a year ago with refurbished Apple TV4's (aka "Apple TV HD") because the old ones didn't support Sling. If you can find a refurb Apple TV HD in Apple's store, it will be considerably cheaper than the 4k version, which is why I went with it (I needed two). I don't have a 4k TV and really didn't want to spend the extra $$.
If you read the forums, plenty of complaints about both the HD and 4K versions. Personally, I would love to have just kept the old Apple TV 3's if they would support Sling, much more stable, better remote and more attractive user interface IMO. Not really interested in games or apps, I just use it to watch TV and access my large iTunes library with home sharing.
There have been lots of rumors about a new Apple TV but many are still skeptical. But if true, this might be a bad time to get the 4k version.
"Apple is working on an updated version of the Apple TV that will allegedly have gaming focus with an updated remote control, a faster processor, and increased storage capacity. Signs of the new Apple TV have been showing up in iOS since January 2020, so we are expecting to see a new Apple TV launch in 2021."
Apple's revamped 4K Apple TV features an A15 Bionic processor, 64GB or 128GB of storage, and HDR10+ support. It comes with a USB-C Siri Remote.
www.macrumors.com