For the Sony Xperia Z5 series, the next firmware update will be rolled out at present. The update is called 32.0.A.6.200 and is now the models of Sony Xperia Z5 (E6653), Sony Xperia Z5 compact (E5803, E5823) and Sony Xperia Z5 premium (E6853) available.
Now, the firmware update 32.0.A.6.200 available is for the new Sony Xperia Z5 series. Should the update via OTA and also PC companion on the models of Sony Xperia Z5 (E6653), Sony Xperia Z5 compact (E5803, E5823) and Sony Xperia Z5 premium (E6853) will be rolled out.
As always, the update in waves is rolled out, so it may take a little longer at one or the other. A changelog is not unfortunately so far yet. It is but to assume that it will bring the usual performance improvements. I assume that the firmware update 32.0.A.6.200 will be available in the next few days in USA also.