Some may have feared that there were no more updates for the Xperia X range, but Sony has updated the handsets with the latest September 2018 Android security patches. The Xperia X and X Compact have seen their build number move from 34.4.A.2.107 to 34.4.A.2.118.
In addition, the Xperia XZ and XZs have seen their build numbers move from 41.3.A.2.171 to version 41.3.A.2.184. It looks like Sony has stopped updates for the Xperia X Performance, as that phone has not seen an update since June. The updates should be rolling out to all regions over the coming days.