While I don't know if it's worth it to buy a 4K right now... I can tell you that in the past 5 years my family has owned 1 Sony, 1 Panasonic, and 2 Samsungs. None of them were 4K
The Sony was the most expensive. And died shortly after the warranty had expired. I googled the problem and it seems like sonys have gone down In quality recently.
The Panasonic is nice but the wifi is a tad slow.
The 2 Samsungs are gorgeous, the cheapest, and have been the most reliable. The only issue I've had has been with the speakers, which are meh. But getting a good sound bar or surround sound is pretty normal for most flat screen tv users.
Anyway, just thought my experience might help. Stay away from Sony. Panasonic is good. Samsung has been awesome (and affordable)