Seriously, don't upgrade your TV, there's no point. If you don't have a 1080p TV, upgrade to that. No sense in shelling out for a 4K TV when most games will NOT be running at 4K. Any graphically impressive games will run at 1080p 60FPS or 1080ps 30FPS with considerable graphics performance.
Your standard 1080p display will get huge improvements to the graphics with the Pro, you don't need a 4K TV unless you really need/want one.
None of the games will be in real 4k. Except for, like geometry based games or something, but the 4k part is an upscale, not an actual resolution increase. I read a thing on it. It seemed like that's a bit if a simplification and it looks nicer than you might think on a 1080tv.
That said, there are advantages worth getting for a 1080 tv, too. You definitely don't need 4k to want this. Youll want this like you'll want any other mid-generation upgrade. It will run your games better. Even non Patched stuff should have better contrast and more vibrant colors. Games with patches for it will look like the pc version on year old mid range rig. A nice, completely nonessential but noticeable difference.
I can make use of a second ps4. I'm setting up a game room in anticipation of my VR system to be named later, which means I'm going to want, probably, to use the old one as a Netflix machine in my bedroom. So, it might also be worth it to add a new tv to the mix anyway. 4k is getting cheap, too. A friend of mine just got a 50" for around 750. Come tax return season, I'll have a couple grand to blow and, god willing, no girlfriend to spend it for me. I'm gonna build the sickest game room you've ever seen.