forget the 4790k, the other platforms will be alot better. the x99 i7-5820k will cost around $120 dollars more for the motherboard & cpu over skylake. if you are planning on 4k, then you should try to get the fastest cpu as possible for your budget. x99 platform also has more memory slots, to allow for more memory upgrades later. for games it shouldn't matter much between any of the cpu's as games are mostly gpu driven now days.
the benefit of the i7-6700k is the 4 cores at high clock rates. after effects will need a little less ram as there are less cores to feed. so if you are tight on budget starting with 16gb of memory, AE would allocate more ram per thread with the 4 cores vs 6 cores. most of adobe's software has poor programming, which leaves parts of the software unable to properly multi-thread. so in those programs and situations the i7-6700k will perform similar or better than the x99 platform. in a few news reports, intel supposedly went a step further with skylake to apply non multi-threading applications across all cores. this shouldn't be needed with 64-bit software, but software companies like adobe that don't properly code, force these kinds of workarounds to fix software problems. the few benchmarks i've seen of skylake on single threading, suggest this new feature isn't working or isn't really there. so perhaps these news reports aren't true, which is too bad.
Thank you! I think I'll be going with skylake, if it doesnt come out by september ill be going with haswell-e x99 haha.
This is purely a budget and timing question. Budget is your decision to make. Timing for the i7-6700 is expected to ship by October, so shipment of i7-6700 systems will probably not happen before November but might be delayed even more.