They both launched at around £260 (
source 1,
source 2) for the top i7. Sure, that quickly inflated to £290, and now is more like £310 and even as much as £340 in places, but that's supply and demand.
As for the temperature issue,
reviews say that's mostly limited to just the i7-6700K. The i5-6600K has fairly average temps. Even when the i7 peaks over 100W on full load, it only gets up to 70-74C using the stock air cooler. Any after-market cooler, especially CLCs with 120/140 - 260/280mm radiators, will have no trouble cooling it. And gaming is more like 83W than 100W, so temps wouldn't even go as high.
Now regarding Kaby Lake, I don't really want to speculate if it will be good or bad. Considering the non-event that was Broadwell and how Haswell "Refresh" (Devils Canyon) only acted as a stop-gap, Intel don't exactly have a stellar track record. And also considering that each gen since Sandy Bridge has only been incremental upgrades, I'm not exactly hoping for much. But if they're ditching older gen device handling/emulation (i.e. support for older OSes) for a more modern architecture, maybe there's hope. Not holding my breath, and I maintain zero expectations, but with DDR3 about to be phased out, PCI-based storage no longer bottlecapping the rest of the system, and the stories of Intel/Micron's Xpoint memory architecture that could completely replace RAM/SSD storage altogether with something "1000x faster".........
Things are changing, the question is when. Each gen of chipsets lets them try out ideas (like how M.2 started at 2x speed in Z97 and is now universally 4x speed). But I don't get my hopes up with any "future products" until it actually happens and gets reviewed.