Like being way late on Broadwell hasn't done any damage. in essence the SP3 should have been Core-M on the low end instead of i3 and Broadwell i5/i7 at the high end and not the same i5 CPU as SP2.Yeah, I'd suspect that it would require some change, but revising the system board and updating the firmware should be doable without significantly impacting the schedule of the bigger bump for the next generation. The biggest impact of the pin compatibility is that the chip will fit in the same physical space so the redesign of the board should be trivial.
It just doesn't make sense that Microsoft would release 3 revisions in 18 months and then nothing for over a year. If they ran into problems with the next generation or Intel was late with Skylake it could tank the entire project.
I currently don't expect Intel to ship Skylake in time for a product release this year. This bubble will pass, albeit painfully, everyone in the Intel pipeline has got the same issues. I don't think ARM will put enough pressure on Intel to force them to dump Broadwell and jump to Skylake sooner rather than later.