Is Boot Loader (SDK 16.0.0, S132 v6.1.1) compatible with application (SDK 17.2.0, S132 v7.2)?

[RVM]

Our company has devices out in the field with Boot Loader (DFU over BLE) and application built using SDK 16.0.0 and Soft Device S132 version 6.1.1.
For a variety of reasons, we are planning to migrate our application to SDK 17.1.0 (or later) and Soft Device S132 v7.2.

The question we have is:
What is the risk of downloading the updated application (SDK 17.1.0 and SD S132 7.2.0) on a device that uses Boot Loader and DFU based on SDK 16.0.0 and S132 v6.1.1?

Our product design is almost identical to the board design included in the SDK distributions.
We use the DFU (over BLE) firmware from Nordic with one extra step to initialize a custom GPIO.

Cheers

RVM

[Turbo J]

DFU over BLE requires the bootloader to fit the softdevice.A bootloader for SD 6.x.y won't work with the 7.2.x softdevice.

Thus you need to flash both new softdevice and new bootloader at the same time - the SD update procedure supports that.