Salesforce has announced that they will be automatically turning on Lightning Experience for orgs that support it starting in Winter 2020. By transitioning everyone into the new Lightning Experience, Salesforce hopes to continue to increase productivity through its efficient and flexible system. The following users will be seeing the “Switch to Lightning Experience” Link:
- Standard Profiles (automatically include the Lightning Experience User permission by default)
- Custom Profiles or Permission Sets that have the Lightning Experience User permission enabled by an admin
- Any Lightning Experience-enabled users working in Salesforce Classic
Anyone that wishes to prevent the auto-enabling can create custom profiles that do not have the Lightning Experience User permission enabled. For users that wish to transition to the Lightning Experience right away, the Lightning Experience Transition Assistant is available with plenty of resources and tools.
For more information, you can read further here.