There's no Newsroom posts or any information about the 2017 iPhone X. Now it's obvious why Apple have removed it from their website: they don't want people buying it over their new phones. It would also confuse customers and affect sales if the iPhone X was listed as well as the iPhone XS.
It makes sense as the XS is the predecessor to the X and improves on minor things from that phone.
So, the only question now is why have Apple kept the iPhone 8 and 7 on their website?
The iPhone 8 and 8 Plus are the same as the iPhone X internally, just have the older iPhone design with a home button. They are the final phones with home buttons, and will be around until 2020. The 7 and 7 Plus have now replaced the small iPhone SE and 6S that are no longer being sold by Apple. They will be removed from Apple in 2019.
However, support for the iPhone X hasn't been discontinued. It will still get over 5 years worth of iOS updates and security fixes each year. You can also still get support with it through Apple and get your phone repaired.
And, for whatever reason, if you wanted to buy an iPhone X, you can from places like Carphone Warehouse (in the UK) and big-brand tech stores that stock iPhones. You'll find it at a discounted price of around £800-£850. Don't get the X if it's being listed as £999 - a better purchase would be the same price iPhone XS!