Skylake is new architechture but has tooth paste (not exactly but you get the point) under heat spreader and because of that will run very hot. Also it's only quad core part. Also there won't be any decent processor upgrades for LGA1151 socket from 6700K. Ever. How do I know that? LGA1151 will get max quad core parts because six cores for LGA1151 would make LGA2011-3 pointless. So upgrade wise 6700K is dead end.
5820K is much faster for gaming if game uses at least four cores and with DX12 we might finally see that. i7-5820K is much more future proof and gains from new architechture are minimal anyway. In 5 years DirectX 12 software should become more popular. Some games, like Star Citizen (will possibly never get ready but anyway), already want hexa core CPU for maximum settings.
Those programmers are probably talking about DirectX 11 that heavily depends on single core performance. That picture tells a lot: http://www.extremetech.com/wp-content/uploads/2014/03/2806.cpucompare.png
So threading does not help because DX11 is not made for threading, DX12 is.
Why more video cards need more CPU power? Better graphic options usually need only more GPU, not CPU power.
Main reason I recommend i7-5820K is because 6700K is overpriced. Previously there was huge price difference between low end and top end platform CPU's. Now top end CPU costs essentially same as low end platform CPU so I'd certainly take high end platform choice with high budget.
The paste under the heat spreader is irrelevant. If it proves to be an issue, it will get changed in manufacturing. What evidence do you have to support what is there now is that bad? Every posted test I've read so far shows the Skylake CPU's running cooler than the 4790K. Here's just one example: https://www.pugetsystems.com/labs/articles/Haswell-vs-Skylake-S-i7-4790K-vs-i7-6700K-641/
I know the 6700K is a 4-core part, I said as much in my previous post. The socket 1150 and 1151 parts represent the "home" PC category of CPUs and chipsets. 2011v3 is a "server" and "workstation" class CPU and chipset. A wholly different category aimed at the business/professional environment, again I said as much in my previous post.
But there are no games now that are using 4 cores, only 2 at most (I believe there is at least one that will use 3 cores). Putting a 6 or 8 core CPU in your system will not run any current, or near future games any faster. In fact, they will be slower because the 4-core line of CPUs run at higher clock rates. 2-cores at 4.0GHz will beat 2-cores at 3.3 GHz, or 3.0GHz, so no, the 5820K would not be "much faster" with a game that could use 4 cores, because the 4790K and 6700K CPUs have 4 cores and they run them at a higher clock rate.
Sure, you could overclock your 5820K to 4 GHz (if it will run stable there) and equal the 4-core 4790K or 6700K, but you can probably overclock the 4-core CPUs even faster, so in the end the 4-core CPUs are the kings of gaming performance. This is really undisputed in the PC world and has been for some time.
DirectX is just an API for accelerating graphics performance, it has nothing to do with the base game code. The program code is where the number of threads used is defined. Game programmers are already telling us that going over 2 threads is extremely difficult, and even in the cases where they are able to get a game to run stable with more than 2-threads, the performance increase is negligible...i.e. not currently worth the effort. Think about it...parallel computing is definitely not new at all. Plenty of other programs have been doing it for a very long time, so why do you think games are still struggling at getting over using 2 cores? Because the programming involved is very, very difficult and the performance gains are minimal.
Even if we assumed right now that a game came out that could use 8 cores, how much performance increase do you think you'd see? I'll bet money it won't be nearly as much as you think. To realize any significant gains with a game that can run on 8 cores, you'd also have to have a proportional increase in GPU processing power and we don't have that right now. At best you'd be looking to add 3 or 4 video cards to your system, but doing that runs into limits on the available PCIE lanes to run them. You can't run 3 or 4 video cards on any current 4-core CPUs and chipsets. Gaming performance has always had a relationship between CPU and GPU power. It takes both to see real improvements in games. Without it, you bottleneck the system at either the CPU or the GPU, otherwise all you'd have to do is slap a Titan X on an older, cheap Core2Duo system and be screaming, right?...wrong. It takes both CPU and GPU for game performance.
Games have to process the code and graphics and the sound and the positional data of other players or objects and then output it all to the screen and speakers at the same time. There are massive timing issues involved. All other parallel processing software doesn't have this issue, so they can easily be multi-threaded.
You don't have to believe me. Go look up Amdahls's Law on parallel computing and see for yourself. Go visit programming forums and see why game programmers aren't expending massive effort to make games use 4, 6, or 8 cores.
The bottom line remains, if your goal is absolute top-end gaming performance then a 4-core i7 4790K or 6700K is the top choice right now, period. The 5820K, or any of the CPUs above it will still game decently well (and most likely acceptably), they just won't out perform the 4-cores in games. Period.
As I also said before, the advantage of having more CPU cores has more to do with using programs that make good use of all the cores, like CAD, photoshop, virtual machines, etc. If you do any of that, or want some good performance with that type of program and can accept a slight decrease in gaming performance, then yes, a 2011v3 based system makes sense, but...if your goal is completely and totally all out game performance, then one of the 4-core i7's is king.
We can compound the gaming issue a little further by stating you should match your GPU make/model to your favorite games because some games run better on NVidia cards and some will perform better on similar AMD cards. There is no one card that will crush everything in every game.
And to compound yet further, performance is going to change depending on the resolution you want to run them at.
The OP specifically stated his goal was maximum gaming performance and he said he had no intentions of upgrading the system, he will use it until it is no longer viable and then buy a new system. In that case his best bang for the buck is to build a socket 1150 based system with an i7 4790K if he is going to build it right now.