Some sources have been saying July but i am expecting an August launch. the gtx 1070 ti is a great card and for 1080p or even 1440p it will be fine for a three years.
You could go for a gtx 1080 and you would get some extra time but the 1070 ti is practically just alike though the gtx 1080 is still better look at benchmarks and check what fps you want and what games you want to play and decide from there or you could wait for the new cards and cross the bridge when you get there.
until