Bull.. you'll see no increase in anything going from 760K to 860K.
Unless of course they run at the same clock speed...as the 860K smashes the 760K clock for clock.
The 760K might OC a little better...but you'd need 5 Ghz to somewhat be equal to the 860K @ 4.7 Ghz...and both values are pretty much a chip lottery WIN.
In bad case scenarios you'd end up with both being at around 4.5 Ghz on both of them..in which the 860K will pull ahead of the 760K.
Anyway...try OCing your 760K first...if you can't get it stable above 4.6 Ghz and you don't want to spend a lot of money...the 860K is a good option since 4.5 Ghz there should equal 4.7-4.8 on the 760K.
Your other options consist of:
Waiting for FM3 socket with Zen. (Not so soon, but probably the cheapest out of the "wait" options)
Waiting for Intel Skylake (Soon, but probably on the more expensive side)
Buying some nice i5 right now if you got some more money to throw around. (Around $170-$200 for a CPU and then whatever fits your pocket for the mainboard...if you don't OC, a cheap board for $50 would do the trick I suppose)
Buying some ancient FX right now, FX63XX or FX83XX are really cheap right now...but not every game might be able to use all of these additional threads...leaving you with NO difference at all if the games run on 2-4 threads...questionable upgrade.
Question is though...do actually NEED more CPU power right now? I mean Witcher 3 even at my resolution is VERY playable on ultra settings for me without the trashy hairworks of course...since even 970s or 980s totally tank in performance if you use it...and all that for VERY questionable hair physics which look worse to me than the non hairworks solution. (lowest is low 30s and "good zones" are in the mid to high 50s for me)
I would imagine that your 760k would equal that performance if you push it to 4.4 Ghz....which should be easy, given that the 700k series OCs like mad unless you lost the lottery. I run my 860K undervolted @ 4.1 Ghz and am VERY happy with my gaming performance...so far nothing was "so" CPU limited for me that I couldn't play it. (Anything non shooter needs to be 30 for me and fps needs to be 60 for me...so far no problem).
To me my most limiting factor would be Vram on those badly optimized AAA titles...so I'd look at a GPU upgrade before a CPU upgrade. Wait for AMDs new lineup to release to see if some prices change imo ^^