massapeal79 :
Gam3r01 :
Again, it depends on what you are planning to do.
To play games in 4k and be ahead for at least 5 years
One 1080 will play games in 4k,buy two if you have money to spare. Buying more than two is a complete waste of money unless you're running a rendering rig or require it to cope with a crazy amount of processing. In regards to being ahead you will only be ahead until the next generation comes out, with the rate tech is evolving there is no GPU or amount of new GPU's that will keep you ahead for 5 years.
The 1080 will most likely allow you to run games on Ultra/High for the next few years though depending on how game optimisation goes. Personally i would wait till Vega comes out, if it performs how its specs say it will then the top end card should be an absolute monster.