I don't expect desktop models will be nearly as close as the mobile SKUs, much like with 14nm's launch.
Larger dies are obviously far harder to produce and much more expensive when on an immature node with a higher rate of defects, and now Intels mainstream desktop SKUs go upto 8-cores.
I think we'll see the low-TDP/mobile (2 cores/4 threads) parts with a semi-paper launch and a few month ramp up followed by the 4-core/8-thread desktop & mobile parts a few months after that depending on how yields improve. The i5's and i7's will likely be at least 6 months behind the original mobile parts hitting shelves, and that could be an optimistic estimate.