SQLServer AlwaysOn Availability Groups in 2014 and 2016
There are plenty of reasons to upgrade to 2016 and even possibly 2017, however if a vendor will not support you on those versions, then the benefits of 2016 and 2017 are moot. It is less risky to stay with a supported version than to take on the benefits of what 2016 and 2017 will bring you.