If you own a Sony Xperia M4 Aqua and are waiting for the device to get the Marshmallow update, here's some good news: the update could be soon rolled out as the firmware (26.3.A.0.131) has been certified by PTCRB.
The current software version is 26.1.A.3.111, which is Android 5.0 Lollipop. So, a bump to 26.3.A.0.131 likely indicates that Marshmallow is coming. Adding weight to this is the fact that Sony has already confirmed that the device will directly jump from Android 5.0 to Android 6.0.
Although an exact date is yet to be revealed by the Japanese company, we expect the roll-out to be begin sooner than later.
Courtesy to GSMarena