As part of the Office 365 message center announcement MC173385, Microsoft has announced that any new or existing team in Microsoft Teams now supports up to 5000 users doubling the previous supported limit of 2500 users.
This change is going to help larger organizations use Teams for a larger variety of collaboration use cases and more than just projects or departments.
To support these change Microsoft also increased the e-mail distribution list import limit to 3,500 from 300.