For a while, it was unclear whether we would see Broadwell on the desktop. With the recently leaked benchmarks of the Intel Core i7-6700K, it seems all-but-certain that Intel will skip it and go straight to Skylake. Compared to Devil's Canyon, the Haswell-based Core i7-4790K, the Skylake-S Core i7-6700K has the same base clock (4.0 GHz) and same full-processor Turbo clock (4.2 GHz). Pretty much every improvement that you see is pure performance per clock (IPC).
Image Credit: CPU Monkey
In multi-threaded applications, the Core i7-6700K tends to get about a 9% increase while, when a single core is being loaded, it tends to get about a 4% increase. Part of this might be the slightly lower single-core Turbo clock, which is said to be 4.2 GHz instead of 4.4 GHz. There might also be some increased efficiency with HyperThreading or cache access — I don't know — but it would be interesting to see.
I should note that we know nothing about the GPU. In fact, CPU Monkey fails to list a GPU at all. Intel has expressed interest in bringing Iris Pro-class graphics to the high-end mainstream desktop processors. For someone who is interested in GPU compute, especially with Explicit Unlinked MultiAdapter in DirectX 12 upcoming, it would be nice to see GPUs be ubiquitous and always enabled. It is expected to have the new GT4e graphics with 72 compute units and either 64 or 128MB of eDRAM. If clocks are equivalent, this could translate well over a teraflop (~1.2 TFLOPs) of compute performance in addition to discrete graphics. In discrete graphics, that would be nearly equivalent to an NVIDIA GTX 560 Ti.
We are expecting to see the Core i7-6700K launch in Q3 of this year. We'll see.