The Broadwell-K launch will bring to new chipsets to the market: the Z97 and H97. Unfortunately, current 8-series chipsets aren't compatible with Broadwell-K so you will be required to buy a new motherboard.
Broadwell-K processors will have 4 CPU cores and support Turbo Boost technology. There will be Core i5 and i7 versions of these products. Core i7 parts will come with 6 MB L3 cache, and will have Hyper-Threading enabled. Core i5 microprocessors will have 4 MB of level 3 cache, and no Hyper-Threading. The CPUs will be compatible with 9-series chipsets, however 8-series chipsets will not validated with Broadwell-K chips.