As an X user, if given the choice today between an X for 900 and an XS for $1000 I’d be getting the XS.
The $100 discount isn’t enough even if the benefits of the XS aren’t huge - the processor and camera improvements are worth that 11% extra.
I think it’d have to be 800-850 before I’d drop down to the X.
In terms of where they go, remember Apple knew they were releasing the XS and not keeping the X as a lower cost model, so there’ll
be a lot less handsets around than normal.