Whether or not the Cayman CAA decides to validate JAA licences in the future is anyone's guess. I can't imagine they will be too happy at the prospect of EASA trying to chuck VP-C Aircraft out of Europe.
What would be the point of not validating JAA/EASA licences? European based Cayman registered aircraft whose pilots have validated JAA/EASA licences will not be adversely affected by PART-FCL. Not to validate would be a case of cutting off ones nose to spite ones face.