OCAD 2019 is just a new name to underline that you are using a software that is constantly evolving and which contains new features and standards. It’s not a new version. If you are on a subscription model, you will automatically receive OCAD 2019 with the latest Service Update and do not need to purchase any new licenses.
For technical reasons, OCAD installation folders, etc., will continue to be marked as OCAD 2018. However, the general strategy is to omit the year in the name of each OCAD edition in the future.