Time will tell though, because Xbox One X could boost the One's sales.
I believe it safe to assume that you will see a nice boost early on with the X model on sale. I also think this will be a deceiving addition to the Xbox One userbase. I suspect early X adopters will make up primarily of existing Xbox One gamers. Those same people who lined up to buy a Xbox One at launch will be back for an upgraded model. This is something that the Xbox 360 never benefited from. Although you could argue that it benefited from selling a lot of replacement consoles thanks to the RROD. Year one for the 360 was pretty bad from a software perspective. It really didn't look like much of an upgrade over the original Xbox at launch. Sure, it was playing games in 720p, but the overall fidelity didn't really separate itself until 2007 when developers really started finding their stride in HD development. 360 also did rather well in the UK, but the Xbox One doesnt seem to be enjoying that success to the same level because of the popularity of the PS4 in that region. Xbox One may be able to replicate the success they enjoyed in the US with the 360, but world wide sales will be difficult to match.