Jump from 1080 to 1440/4k, worth it right now?

Currently running rig with fx-8350 and gtx 970, would upgrading to a 1440/4k monitor be feasible/worth the money? or is more graphics horsepower required to make it worth while?

I ran a 670 at 1080p for a while, just recently jumped to 1440p, still runs most games. I would say its worth it, but plan to upgrade pretty soon. Especially if your really into playing AAA titles.

I'd wait for a few of the new monitors to come out around the time of the 300 series release.

Wait for cheaper monitors and I think you could get more out of it.

Meanwhile, you could try messing around with the Dynamic Super Resolution feature of your video card.

Well 1440p and 4K are two very different things.
4K I wouldn't recommend just yet. The monitors are still quite expensive and they aren't the best. Especially as most are TN. Plus your 970 will really struggle to push games at that resolution. So for 4K wait for better cheaper monitors and a better GPU.

1440p is a different story though. 1440p isn't new anymore and in my opinion it is the best resolution you can get right now. Not as sharp as 4K yes but still very nice looking. You don't need scaling which is nice. Most GPUs can push it well in games. Plus you can get nice monitors for reasonable prices.

It actually makes a nice difference doensampling from 4k to 1080p

Right now, I'd jump to 1440p, these monitors are getting more and more reasonable in price, and the GPU performance to power it is already here, a GTX 970, a R9-290/R9-290x will do just fine at this resolution.

4k? no so much, you still need two GTX 980s or Two R9-290/290x GPU's to even have a remotely decent experience.

for 4K i'd probably wait one more generation or so, so, probably 2016 or 2017 to jump on the 4K bandwagon, cause by that time, AMD and Nvidia will probably have a High End that will do it just fine with one GPU.