Silverlight page says that it won't work on all Mac browsers after March 2017, but the question about future of OOB Silverlight on Mac is simply unclear.
So the question is, how do OOB apps work on Mac? Do they use Safari to run, and are supposed to stop to work after this March 2017? Do they run independently from the browser and will continue to work, even after browser support isn't available anymore?
According to this article a user is required to install the OOB version from the browser. Presumably if browser support is removed users will be unable to install the OOB applications. It is not clear what happens to users who have already installed the OOB version.
https://msdn.microsoft.com/en-US/library/dd550721(v=vs.95).aspx