vandalblue :
See below my specs, and u have an 4k monitor right now, so i just want to keep the cutting edge and most powerfull parts trough next gens, and, dont like to use sli, there so much games/apps that dont use dual gpus
Well really depends on what games you play to use SLI, although I would have to agree that multiple gpu's are hardly used in most games (well not used well).
Well to run at 4K over 60fps, without SLI. With a single gpu you may be waiting a couple of generations. Maybe Volta or futher on.
Remember as gpu's advance games also get more and more demanding, so even if a top of the line card in a couple years can run Witcher 3 at 4k at 90fps. Another newer game that is even more demanding by then could only run at 50fps.
So in my opinion a great upgrade would be volta or even futher, if you always want the cutting edge I'd wait for the Titan to come out
and then always wait for the top of the line card come out every generation.
It is really hard to future proof at the speed of the graphics industry
-good luck