Hi there 
We are currently developing a game and are considering between Wwise and Fmod.
One of our consideration is backward compatibility of generated sound banks - will current sound banks, generated under current Fmod version will still be compatible, if we decide to upgrade to next Fmod releases (both studio and integration, obviously).
Or will we be forced to regenerate all sound banks, because of compatibility issues?
A bank built in any version of FMOD Studio can be loaded by all later versions of the FMOD Studio API.
In addition, a bank built in any given version of FMOD Studio can be loaded by other versions with the same major and product version numbers. A bank built in FMOD Studio 2.00.03 can therefore be loaded by FMOD Studio API versions 2.00.00, 2.00.01, and 2.00.02, in addition to all later versions, but not by FMOD Studio version 1.10.14.
Incidentally, while new patch versions of FMOD Studio only contain bug fixes, features, and performance improvements that do not alter behavior, new major versions can and often do include changes to behavior. We therefore recommend that you only upgrade to a new major version of FMOD Studio part-way through a game project if your game project requires a feature only found in the new FMOD Studio version.