Hi Mohib,
We are looking at upgrading 4.0 to the latest stable version. If 4.3.1 is available, we would like to with that (we prefer to go with x.x.1 onwards)
The background on the upgrade, we are still at 4.0 as the latest upgrade includes a JDK upgrade which affected the kerberos deployment with the customer's AD (which was stuck at 2008R2)
They have recently upgraded their AD and we are looking at upgrading their Gluu deployment to the latest.