It's not that simple:
1) Skylake-K seems to be delayed to late 2015. Based on current roadmaps and rumors, it will take until May-June 2015 before Broadwell-K launches. After Intel is said to release Skylake-S. A multiplier locked Skylake would have a tough time beating overclocked Haswell.
2) If you are going to make the argument of waiting another year for Skylake-K, then you'd have to compare it with a BW-E, not with HW-E. Someone who is looking to upgrade now is not going to wait another year. Also, you assessed that the value of a $1000 5960X is poor but ignored the nearly $400 5820K. Those buying the 8-core are surely not just gaming. If 5960X overclocks worse than 5820K, these gamers would consider the 6-core instead.
3) It depends on how long you want to keep the main platform for. If you don't think that in the next 3-4 years there will be major AAA games that could benefit from 6 cores, then 4790K is the right choice. But if we look at performance of overclocked 2600K vs. Overclocked 4790K, in 3.5 years there is hardly a difference in performance in games implying that the difference in clocks and IPS is almost entirely absorbed by GPU bottlenecks. This suggests that a gamer doesn't need to upgrade the CPU platform every 2-3 years but instead every 4-5 years. I would imagine next gen games in that time would benefit far more from 4.5Ghz 6 core Haswell than a 4.8Ghz quad 4790K or even Skylake-S. Again, since Skylake-K is now ways off, I don't even see how it's relevant to compare to HW-E.
4) If someone wants to go 2x SLI + M.2 SATA or Tri-SLI, the X99 chipset is the go to system.
All in all with 5820K dropping to almost $400, and DDR4 pricing dropping already, the price difference between going 5820K and 4790K could approach $200 or less which is not a lot over 4-5 years of the CPU platform's life. Obviously if someone has a strict budget, it is better to put it into a faster GPU if gaming is their primary motivation. But in that case, i7 4770/4790K isn't worth the upgrade yet for 2600k/3770k users either. Also, I don't think X99 platform targets users with 4770Ks either. It looks a lot more attractive for someone on 1st generation i7 or 2500K who is looking for a large increase in performance after 3.5-6 years of using their old system.