That may be, but as long as he can _assume_ 2060 will cost $100 more and Vega can be had for less than it actually does, _then_ Vega becomes the better pick.
It is not inconceivable 2060 might be sold at a markup, at least initially while Vega gets a price cut. But that is just not the data we have today.
I don't know about US but in Europe Vega56/64 as well as GTX1070Ti sell for prices starting at about 50€ under MSRP - assuming MSRP in € is the same as $ as it has historically been. Vega56 for 350€, GTX1070Ti for 400€ and Vega64 for 450€. GTX1080 and GTX1080Ti are clearly running out of stock if not already out. On Nvidia side, 1070Ti is on its way out as well. Not sure about Vegas but the way prices behave the current situation seems to be a clearance sale on these.
RTX2070 can already be bought for under 500€. Nvidia has clearly trying to bring retailers into the fold after all the talk about high RTX2080/RTX2080Ti prices. RTX2070 was at MSRP pretty much at the point of release and RTX2060 will likely follow the same pattern.
Given all this as well as the Freesync/G-Sync Compatible thing, other than not buying an Nvidia card on principle, Vegas are really running out of reasons to buy them.
Looking at wider state of things what concerns me is RX590 at $279. This was less than two months ago.
This is also why Turing is in some ways an opportunity for AMD to at least do some catching up - the 2080ti isn't really a realistic competitor in the market and its easy to price royally under it with somewhat lower performance.
RTX2060/2070/2080/2080Ti are spaced fairly evenly apart. Looking at the TPU performance summary charts, 13-16% at 1080p (where things are probably not GPU limited), 18-21% at 1440p and 20-21% on 2160p with RTX2080Ti being whopping 28% faster than RTX2080 as a bit of outlier. It will be difficult to find a window there, especially considering RTX2070, RTX2080 and RTX2080Ti are all separate chips with possibility to cut one down to fill any gaps
There are things AMD can go for, primarily price but also more memory. However, it will still need a competitive GPU at the core.