Intel learned long ago, with the creation of their enthusiast -E platform and the staggered release schedules resulting thereafter, that having multiple architectures fielded at the same time does not cause the sort of market consternation or consumer trepidation that you are envisioning.
If technically savvy enthusiasts, about the only portion of consumers that would know an IB from a SB-E SKU, don't care that IB was out while they were busy buying up SB-E chips, then surely Intel has little to be concerned with when they are selling BW chips in laptops and SL chips in desktops to an even less technically literate consumer demographic.
Right, I think what Intel is somewhat careful of, is not putting multiple architectures against each other within the same product. I don't see them pitting ~15w TDP BGA Broadwell vs 15W TDP BGA Skylake for instance.
I have a feeling, by Q4, 2015 we will see something like:
LGA unlocked 'K' >80W TDP CPUs - Broadwell
LGA locked CPUs <80W TDP CPUs - Skylake
BGA > 30W TDP CPUs - Broadwell
BGA < 30W TDP CPUs - Broadwell
BGA <5W TDP CPUs - Skylake phasing out Broadwell
I wouldn't think Intel would phase in Skylake until Broadwell's shelf life reaches ~9 months for a particular market. They might not even bother with >30W TDP Broadwell, might just skip ahead to Skylake. Apple seems to be the one pushing Intel the most for new tech, and they don't deal with >30W TDP CPUs anymore. All the OEMs are racing to the bottom price-wise, their probably happy to keep Haswell until Skylake is ready.