Oh sorry I meant 1660ti or used 1070 . Its late. The 2060 pulls ahead around 10 to 20% in various games. If you do go ahead and buy the 2060 I would strongly recommend upgrading to a 1440P monitor, trust me the difference is huge over 1080P but otherwise I woudl save your money and get the 1660ti.
The issue with future proofing is that technology is unpredictable, I bought a 7700K CPU then AMD announced Ryzen and suddenly Intel chips got more cores for lower costs.
My new core belief on building computers is price to performance for at least 2 or 3 years, beyond that its insane to try and gamble. I would wait for AMDs NAVI announcement which I believe will be Monday.