Soon Rob, no exact date released yet however. And as I eluded to earlier with my own experience buying the x79 and 3930k and 3820k chips, the price on the MB and CPU's didn't drop much, even to this day, and it was late Nov 2012 I built both of those systems, so Chalenge does raise a valid point. Unless you're looking at the higher end 780s, or even the 770s, the prices may not come down all THAT much, it is hard to predict.
I guess my point is you may be able to buy slightly newer and more current stuff if you wait a short period, as the newer x99 boards may not be all that much if any more expensive than the current x79, if as Chalenge mentions, the prices don't drop much. You'll be better off getting the latest stuff if it is around the same price, as it'll be upgradeable for a longer period of time. Example, they aren't going to be making any new CPUs for my 2 390$ motherboards, the x79 Sabertooth and ROG board. However, the new socket 2011-a or whatever they'll call it, the x99, will have most likely another round of new CPUS in the future, just as the x79 did with the 4820/4930 and whatnot.
All I'm saying is unless you need it NOW, waiting for a couple months at most may either save you a bit of $, or at the very least let you get into the latest tech motherboard/cpu for close to the same price as the x79 setups now, as again, the $ of those haven't changed a whole lot over the last couple of years. One of two things will happen - they'll either come down now as they are phased slowly out, OR they won't, in which case, like I said, the newer x99 stuff will be close enough in $ to be worth the extra few percent it may cost you to go with the most current, and hence the stuff with the most longevity upgrade wise. That's all.
The rumors are flying that it'll be the end of August or mid Sept at the latest that the new Hawell-E Intel x99 platform stuff will be launched, so it won't be too long now. Some of the rumored eVGA x99 MB prices are in the 250$ or less range as well, so like I said, compare that to the current x79 mb price in your OP link, and you'll see what I'm getting at.