The Sony Xperia XA Ultra update to Android Nougat is in full motion now with the update rolling out to users. The update is version 36.1.A.0.179 and is based on Nougat 7.0. The update follows the release of the June Android Security Update for several other Xperia phones on Tuesday.
Right now the update to Android Nougat is happening in European variants of the XA Ultra but the expectation is that other country variants will see the update soon. If you have the XA Ultra, you can check for the update manually in the settings of the phone.