Hi Jen,
Thanks for checking out our plugins!
You are correct that after the subscription expires, you would no longer be able to access plugin updates and premium support without renewing the license. However, the existing plugins on your site would not be affected. You could still create new events. Going forward, if you continue to update WordPress and other things on your site without updating Events Calendar Pro, you will eventually run into compatibility issues.
Please let me know if you have any other questions!
Thanks,
Jennifer