broadwell from what i gather will be a soldered on to the motherboard solution if intel get there way. although the motherboard manufacturers are trying and maybe succeeding in changing intels stance on this. if ddr4 comes down in price quick enough then theres no reason why intel wont add it to there linup, but it will all depend on how haswell e sells as to how quickly the price of ddr4 drops.
ram manufacturers dont want to switch over to it any time soon because the build cost of ddr3 ram is so low and its getting so fast @3000hz+. while ddr4 will be relatively slow in comparison at release, but will cost a lot more to produce. and the fact that ddr3 is so fast means they cant really justify the premium on the initially slower (but more bandwidth) ddr4, so would have a hard time recouping inital costs.
1 other thing, its taken them 4 years to get from ddr3 1066 up to ddr3 3100+, it may take just as long to see comparable ddr4 bumps.