Well, the 5820k would have the same number of lanes as the mainstream platform (4770k etc) and would cost roughly 300$ if pricing maintains from the 4820k.
That trade-off is well worth it. 16+8 (16 cpu, 8 chipset) PCI-E lanes has never been a detriment for me, the only way in which it is detrimental for most users is if you want quad SLI. Generally speaking, quad SLI requires a PLX chipset motherboard with 40 pci-e lanes (16 via cpu, 24 via chipset) which can give you quad SLI. Or you can get the 4930k which has 40 lanes inherently both through cpu and chipset (32 via cpu, 8 via chipset)
I do not care about quad SLI. Therefore I do not care about 40 pci-e lanes. I'll happily take the 16 cpu lanes and 8 chipset pcie lanes for a 300$ hex core. Are you kidding me? If that chip is 300$, and unlocked, it's going to sell like mad. Probably would give the HEDT platform a boost, and i'd be one of the first to buy it - whereas I typically buy the mainstream platforms.
Again, if the 5820k is around 300-350$. It's going to sell like mad. Most people do not need 40 pcie lanes (again, 32 cpu / 8 chipset) unless they want quad sli. Most people do not want quad sli. WORTHWHILE tradeoff IMO. This will all depend on price. I do hope the 5820k is 300$ as is the 4820k. If it is. Count me in.