So what happens when SHA1 falls out of support?
If you have your SBS (and Essentials) servers set up properly with a third party SSL cert and not a self signed cert, nothing should happen.
SBS can support higher SSL certs than SHA1. If your SSL cert is soon to be out of date or blocked just go to CheapSSL certs or Godaddy or wherever you get cheap certs and buy a third party SSL certs. No one should be using self signed certs anyway.
SHA1 Deprecation: What You Need to Know