Future of SelectServer licensing?

I found out today that my organization has a number of users who are still using MicroStation SS4.
I have read through this website in an attempt to establish what Bentley plans for the future of SS licensed products.

I know that SS is in the "sunsetting phase" but I have no idea how long it will take for the sun to actually set, and SS to no longer be available.

Some of the users have mentioned incompatibility between SS4 and SS10. I am in the process of attempting to troubleshoot with them to see what (if any) obstacles stand in the way of the upgrade.
In the meantime, it might be useful if there were an updated timeline I could share.

Thank you.