Ehh... maybe. Video likes to eat CPU, and 4k eats more before breakfast than other videos eat all day.
Skylake is the future, not Haswell. I have the new i7-6700K, and it's easily faster than the i7-5820K. Most video operations are single- or dual-core, so the main factor here is raw clock speed. It's a 4.0+ vs a 3.3+. So the 6700K in practice is about 25% faster, regardless of benchmarking (mostly non-video use).
And with Skylake, all other hardware must change: motherboard, RAM, etc.
I'd even suggest putting the video on a scratch SSD drive for editing, and only store on HDD when done. That's what I'm doing. That removes most I/O bottlenecks, which, for this exact use, is the main video bottleneck these days.
The Noctua D14 cooler is far nicer. It makes no noise whatsoever with 1 fan (all it needs) and the noise adapters. It's easily the largest part of any computer that I've ever had, going back 30 years.
I'm using a pair of 1TB SSD Samsung 850 EVOs.
That Seagate 4tb is currently the best drive. I have one now, and the other is forthcoming.
Check out the Antec Three Hundred II case. Several members of this forum like it, as well as the 300 before that.
I just finished making all these decisions myself, back in October. My main system motherboard is having problems, and it was time to upgrade my 6-year-old AMD Phenom II Quad. Total cost was somewhere between $2k and $2.5k (USD). I'm hoping to have it for 5-7 years (~$35/month max for life of the system).
Just an alternative to consider...
