If you start with the Professional edition in Unity, you are able to switch to Unity Expert Edition. However, this will require additional development work as the two plugins have some differences.
Please visit the table here for a detailed comparison between the Expert Edition and the Profession Edition.
Keep in mind that the Expert Edition can be accessed via the Trial and Enterprise license only, so a switch means as well an additional cost.
Should you have questions, please contact us via sales@wikitude.com.