Full upgrade, or GPU only?

Talk me into/out of doing a full upgrade, and instead just dropping real dime on a 980ti (or waiting for Pascal to see if I can get more performance for similar/less)

I'm not in a particular rush, but I did get a 1440p monitor for Christmas and my GTX 570 isn't able to push high settings for FO4 at that resolution, and I can't imagine it will be able to make it work for any modern games.

I tend to play about 2 years behind for non-gottahavit releases. Usually when steam gets cheap!

My current build is pretty much the quintessential buildapc gaming build from 3-4 years ago.

i5 2500K, GTX 570, 16GB of RAM on an ASRock Extreme4 mobo.

Do you think there's any real reason to bother with upgrading the CPU/Mobo/RAM at this point? As near as I can tell, I'm not getting CPU bottlenecked at all under any circumstances.

I should add that if I do a full upgrade, my budget will almost certainly not allow for a 980ti, would probably need to keep the GPU to whatever falls into the $300ish range.

My current thought process is that I'd be best served getting the GPU now, which will still be viable for a few years, and then upgrading the build when there is a significant performance increase to be had from whatever CPU fills the new i5 role at a similar price point.