It wouldn't be surprising to see these brought foward, it's basically trivial, Coffeelake sounds like it's 14nm refined marginally again. I wouldn't be surprised if it's literally SKylake again with a light clock bump.
There is no 14nm +/++, every process gets not particularly close to it's theoretical best case sizing at first then iterates a couple times to get closer. IE 14nm is iirc 64nm metal pitch, in reality the first iteration is probably more like 72nm, then it will get tweaked and they'll reduce the design rules to 69nm, then they do it again and move to 64nm. It gets smaller, or stays same size with more spacing, less leakage and better clocks. Intel just decided to make a bigger deal and brand these tweaks/improvements because 10nm is taking ages and they want people to upgrade so they make it sound bigger/better.
Skylake started as a 122mm^2 chip, at 6 core skylake was possible from day one of Skylake being available, the cores take up only around 40% of the core, so adding 2 more cores would probably only make a hexcore around 140-145mm^2 range. That is trivial die size wise. How long have they been making the 250mm^2 Broadwell-e's.
Kabylake is a new Skylake stepping on the marginally tweaked process, Coffeelake might well just be Skylake with potentially another tweak or potentially not. We're talking about essentially new steppings and rebranded chips excluding a hexcore they've been holding back for 2 years because they wanted to milk profits on smaller chips. They could have made the hexcores 2+ years ago easily, so bringing it forwards 6 months is stupidly easy. In fact even if the so called 14nm '++' isn't ready they can just make a hexcore on 14nm '+', rebrand the lower two, add 100Mhz to the lower chips then in 6-12 months they can release a new bin of those chips with a new stepping.
The only interesting thing about it could be pricing. Somehow I just can't quite see Intel dropping in the hex at 7700k pricing, the 7700k at 7600k pricing, etc. Nor do I think they can do this without better prices. They are losing sales because of price/performance to AMD. I'm guessing the new chips will move down a half a price point then make the hexcore another £50-80 on top of current 7700k pricing.
