Is FMOD now complete on the cryengine?
It will be with the release of 5.6.
What is the FMOD upgrade in version 5.6?
We implemented the ability to simply localize between different languages with Fmod in 5.6 and added support for streamed assets on top of it.
The Fmod GameSDK project is almost incomplete.
Correct, it is not as extensive as the design done in Wwise.
Will be updated in the future?
As GameSDK has not our focus anymore beyond minimal maintenance it is very unlikely.
In general we recommend to create custom audio projects as the GameSDK ones are naturally more of a minimal showcase on how things can be done. This is especially reflected through the fact that no original assets are available for those projects that would allow customization and with that recompilation.