I agree, wise thing to do would be to wait until Big Navi cards are out and benchmarks are available.. I believe it is a price game from there on.
Also, you never know, what all AMD brings to the table as surprise for eg. something that can be compared with DLSS from Nvidia
They have been touting that RDNA is going to be a game changer similar to their Zen architecture for CPU. I understand it is easier said than done but then you never know with AMD.
If they can do it to Intel after a decade then they can do it to Nvidia as well.