vegetaleb wrotePCandparts has already some Skylake mobos, though overpriced as the CPU itself is not here yet.But if they have these mobos it means the i5 6600k is not far :)
The i5 6400 and 6500 are not yet out in the US, most probably by the end of this month, so we could bet to see the 6600 by the end of October (unless they finished the old i5 stock and bring skylake sooner), and the 6400-6500 by the end of November.
The actual mobos are overpriced because not all models are here and specially the CPUs but I think in December their prices will drop by 30-50$ as broader range of MSI and Asus will be here
If you want to get an i5 6600K, get it from r/buildapcproxy, they can get it to you from Microcenter, and since shipping a CPU doesn't cost much, you'll be able to get it for less than what you'll pay for it here, that said, CPU prices here are pretty reasonable, it's video card, case, PSU and mobo prices that's inflated, that said, Z170 are actually pretty well priced compared to the US considering that something like the ASUS Z170 Pro Gaming cost like $189 here and like $167 in the US, I'd pay $22 more for the board instead of getting it for $22 cheaper and paying more than $22 for shipping.