should I buy gtx 1080 if I only have a fullhd monitor 144hz 1ms?

Solution
If you don't plan to update you monitor before your GPU then no, you don't "need" a 1080. If you want to use features like supersampling in new games then I would highly suggest that you do get a gtx1080. A gtx1070 wont be able to render all the pixels required for SS at anywhere near 144hz. (I have a 1070 which is probably ideal for 1080p 144hz) If you do plan to look at a new monitor in the next 5 years (4k is coming down in price faster and faster) then yes I suggest you invest in the best GPU you can find/afford.
If you don't plan to update you monitor before your GPU then no, you don't "need" a 1080. If you want to use features like supersampling in new games then I would highly suggest that you do get a gtx1080. A gtx1070 wont be able to render all the pixels required for SS at anywhere near 144hz. (I have a 1070 which is probably ideal for 1080p 144hz) If you do plan to look at a new monitor in the next 5 years (4k is coming down in price faster and faster) then yes I suggest you invest in the best GPU you can find/afford.
 
Solution
I think it's probably a good idea to wait to see if there are some deals on Black Friday. This time of year it's always better to wait and see. The farther we can get from the mining surge the better. Stocks will recover and prices will drift down with time. I'd be surprised to see a 1070ti launch at 439, considering the cheapest 1070s are 419 and the common price is 479(newegg), but its possible .