Hi Alain,
Good question! Yes, Events Calendar is actually an extension of The Events Calendar and both plugins run together. Event Calendar PRO draws off the same code as The Events Calendar but extends it with a few more features, so you will likely see no compatibility issues if there are currently none with The Events Calendar.
The best thing to do is test it for yourself, so we do offer a full refund on all purchases within 30 days with the receipt. That should give you some time to give it a test drive to make sure all runs smoothly.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff