I'm expecting 4.5GHz base as minimum line for Kaby-X, also solder like all the HEDT line, otherwise there wouldn't be a reason to wait six months when 7700K will be already 4.5 on some mobos with minimal tweaks, like when enabling turbo on all cores.
It's pretty obvious that they are going for something like the FX-9000 series and trying to squeeze every MHz out of the process, so it may reach 5GHz but stop dead there unless you go on water or crazy volts.
Yeah, and if you look at it from a biz perspective, Intel has every incentive to produce a product that they can charge more for on the HEDT line. Motherboard makers probably happy to be able to sell higher ASP/higher margin HEDT boards to customers, too.
Also, once Intel has sold customers their first "hit" on HEDT with a high performance quad core, they may be tempted to upgrade down the line to a higher core count product. Not only does Intel make more money from selling that initial, hyper-clocked KBL-X, but it could very well rake in additional cash from people upgrading CPUs on the same platform.
This is a very good strategy and I'm actually feeling kinda dumb for not thinking of it myself. I thought Intel might just phase out mainstream altogether for enthusiasts and only sell Xeon-derived parts to said enthusiasts. Didn't think of taking a mainstream die and putting it into an LGA-2066 package!