At least that is a claim from kitguru who states that sources close to them told them just that. And 'they' would be the channel, and the channel partners are thus etailers and distributors. Which again in the end remains a bit of a speculative thing to say eh?

We do know that Dell will be taking preorders for new Ryzen Threadripper Alienware PCs starting July 27th. The new info suggest that Threadripper will launch around 10th of August:

From what we have heard from sources close to KitGuru, AMD should launch Threadripper around the 10th of August, after moving the date from a late July launch. This is what we have heard through the channel and if true, would mean we will be seeing AMD and Intel square up once again, this time in the HEDT market.

So that means Threadripper and Skylake-X i9-7920X (the 12 core part) would launch in the same month. Intel however needs more time for the 14, 16 and 18 core parts. AMD will release at least the 12 and 16 core units. Meanwhile a Ryzen Threadripper was spotted in the Primelabs database. Here a 16-core Ryzen Threadripper 1950X was seen with a base clock of 3.4 GHz (boost not shown). 

AMD Ryzen Threadripper Launches around 10th of August