The program will NOT stop working on that date, it will continue working until 2099 and it will NOT require you to get a new license file, so you just go on using it. 

You will be eligible to contact us for any support until that date, after that we are closed.

Will the "TSMManager" software then be license-free and could more Storage Protect servers then be included in the monitoring?
>> It will not be license free (accessible for all), but we recognize the necessity for existing customers to expand and will probably make upgrading an existing up-to-date license free, but it has not yet been finally decided how to do so. More details will be available when we near 2028.
 

Is it advisable to purchase additional licenses beforehand in order to be able to monitor a larger environment later?
>> See above answer, but simply put, no.
 

Can an updated TSMManager version be expected after the announcement of the end of support?
>> Yes, if relevant from now until 2028, we will make updates, but the development stops in 2028.