4790k or any other Core ix 2xxx/3xxx/4xxx/5xxx series CPU s do not support DDR 4 RAM. https://ark.intel.com/tr/products/80807/Intel-Core-i7-4790K-Processor-8M-Cache-up-to-4_40-GHz
If you want DDR4, then you need Core ix 6xxx/7xxx or the newly announced 8xxx series CPU and a matching motherboard.
Since you will need a new CPU, motherboard and RAM, it is best to wait for Core ix 8xxx series CPUs and Intel y3XXX series motherboards to be released.
1) new release means you can get older mobo/CPU cheaper
2) it is reported that the new Core i3 8650k will have 4 cores and have very close performance to Corei7 7700k for gaming and will be less than half of the price
3) if you still want to pay full price, new Core i5 and Core i7 CPUs will have 6 cores, instead of 4 at the same or less price ( and upt o 40% more performance in multi threaded tasks if you believe Intel )
So, wait for 2 months or so before acting.