I think your main issue will be that an I7 2600k still runs on PCIe 2.0, and DDR3. A PCIe 3.0 GPU will definitely work in your system (I ran an Rx 580 in a similar system (with a 2700k)). However, don't expect stellar performance.
I do think you can run most games at 1080p in that configuration - just not on highest settings. 1440p I don't think you'll be able to.
So, it is up to you what you want. In my opinion the GPU market is way too hot right now to be sensible to invest money into. But, if you happen to have a 6500(xt) and bought it at MSRP, I don't see why not.
If you don't have a 6500(xt), I would wait until the second half of this year. Things "should" calm down by then. If you don't want to wait, either try to find a used graphics card at a bargain price, or focus on other parts for now.
(but beware, AMD is switching sockets, for the first time in 5 years, the second half of this year)