If you wait, go into it with the expectation that the Zen cpu around the price of a 6700k will be slightly slower, will probably be a bit less, and overclocking is completely up in the air. If its better, wahoo, but if its that or less, you know what your getting into. By December, hopefully we will know for sure the stock clock speeds and the more specifics of the part, but don't depend on it. But if you do wait until December to build, scrap whatever you plan today and remake it. There is a laundry list of things that can change between now and then.
but in any case I'd suggest an RX 480 with a free-sync display, the display isn't much more than that one, might go on sale again sometime before then as well
Kind of do, because neither a 480 nor 1060 can saturate a 1080p 144hz display for AAA games, so you'll be running below the 144hz refresh rate of your display
That is dependent on where you get the board and the cpu.
If you live near or pass by a Microcenter, check out the clearance shelf as they have board with open box. Otherwise check the buildapcsales subreddit for daily deals
A precaution you should take is to check the box for any missing parts. If you are still paranoid ask for a reason why it was returned.
I got my Asrock x99 board (open box, no issues) for $159 and my 5820k from Microcenter ($30) discount for buying the cpu and motherboard.
at best zen is by amd's own admission weaker then skylake. also rumors are am4+ motherboards should be for sale in october but zen cpu's may not be released till January / February. so you'd likely be stuck with a lower grade A12 or athalon cpu untill then.