My 4k monitor will be coming at the end of June and I also own a gtx 980 but I'll be upgrading to a 1080 ti before my monitor comes.
If my CPU does hold me back from getting 60fps in the games i tend to play on PC I'll just upgrade to the 8700k/2700x. The reason I'm putting off upgrading my CPU is because i either want to buy the 14nm 8 core or the 10nm CPUs intel is releasing next year.
If my 3570k can do the job at 4k until then, then i see no reason to upgrade
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