The FW file you download from our website with DD2.0 link is a patch for DD2.0.
After execute the exe file, you will get BNO055 latest FW (.hex) file under "C:\Program Files\Bosch Sensortec\Development Desktop 2.0\Firmware" which is under the installation folder of DD2.0.
If you wire out the nBOOT_LOAD_PIN (pin 4) to host, then it is possible to upgrade FW also via the host interface.
We are planning to release a example code for FW upload and the application notes.
But in current phase, you still need to contact your local support channel to get those things.