Dear Christian,
As an Independent Advisor and community user, I'll help you with your question.
Your users will have not impact in his access, they can continue using Microsoft Teams with his Microsoft Teams Exploratory license.
By other hand, about Microsoft Teams Exploratory, you have to have in count below information:
"How long does the Teams Exploratory experience last:"
The Microsoft Teams Exploratory experience is available at no additional cost until your next agreement anniversary or renewal on or after January 2021. At that time, end users on a Microsoft Exploratory experience license will need to move to a paid license that includes Teams. Any Microsoft Exploratory experience licenses initiated after that will remain available at no additional cost until your next anniversary or renewal cycle.
https://docs.microsoft.com/en-us/microsoftteams...
Regards,
Renzo.