Hi @nabru and thanks for your query! If you are using the 4C Eye Tracker, then more recent versions of the SDK do indeed include additional features such as head tracking (does not apply to the EyeX Tracker) and of course various minor stability and bug fixes.
Naturally we would always recommend to use the latest release of our software to stay up to date and avoid potential development issues. However, as you indicated that you are only using behaviourMap and HasGaze and assuming that the program itself works without issue, then there would not be much incentive to migrate at this stage.
If you would care to go into more detail regarding your project intentions such as targeted platform, future features, etc we would be happy to provide further advice. Best Wishes.