Overkill as in it is more power and cost than needed. It won't harm anything, but it would be kind of a waste.
Here are some benchmarks (scroll through the next couple of pages):
http://www.tomshardware.com/reviews/nvidia-geforce-gtx-980-970-maxwell,3941-8.html That's a reference 970, which means with the slight overclocking that comes standard on MSI, ASUS, Gigabyte, or EVGA cards, the performance will be slightly better.
As you can see, the minimum FPS in all games is right around 60, with average being a good bit higher than that.
As for future proofing...I'd suggest getting a motherboard that supports SLI, and if your budget allows, a 750W power supply (at least get the motherboard...the PSU can be gotten later). The extra $200 you save by getting the 970 instead of the 980 should be enough for at least one, if not both of those. Then if ever a game comes out that you wish had better performance at 1080p OR if you decide to get a higher resolution monitor at some point, you can just put in a second 970 and be all set! (Two 970's in SLI will do most games at high to ultra settings at 4k:
http://www.guru3d.com/articles_pages/geforce_gtx_970_sli_review,21.html )
Random_Coffee: Is there a big difference between the different brands? In the store I'm using, the Asus-model cost less than MSI and EVGAs versions of the card.
There's not that big of a difference. Slightly different clock speeds, and different coolers, but they're all good. I personally am going with the MSI as it seems all around the best, but go with whatever's cheaper cause there really isn't much difference :)