If you are playing FPS like CS GO then 1070ti is good for 144. But it will not be that good for others in coming years.
Here is some more evidence how close is the 2700x is,
https://youtu.be/ryzCY2eOdKM
In near future 2700x can breathe a bit more than 8700 for sure. Just look how stressed the king of gaming 7700k is right now for all the recent open world titles. 100% all the time.
If anything is faster than 2700x with some practicality is 8700k with it's insane over locking headroom. Pls don't tell mid to low setting comparisons.
Long story short, I would recommend you to get 8700k+1070ti or if not possible then 2700x+1070ti. 8700+1070ti is less future proof than 2700x+1070ti. Just my suggestion afterall. Time will tell the truth. Besides ryzen platform will also give you better upgrade path as well.