Practitioners always need to be concerned about a spouse dying before the divorce is final. The fix here is simple, and most of us do it. Put a clause in agreements waiving any rights the other may have in a statutory share. That is effective in most states, including Massachusetts.
Similarly, in most states, including Massachusetts, divorce revokes revocable dispositions to former spouses in wills and revocable trusts.
Separation, of course, doesn’t revoke any of this. So, if you are going through a divorce, ask your attorney about changing some of your estate planning documents.