Many married couples separate from each other long before they get divorced. They need to redo their estate plans when that is the case.
If you and your spouse get divorced, estate law is good at recognizing that you probably no longer want your ex-spouse to inherit your property.
If you do not rewrite your will and your ex-spouse still inherits under it, then the law will assume that you meant to do so and constructively write the ex-spouse out.
If your ex-spouse is the beneficiary of a trust, it is much more difficult to change the trust.
Even more difficult is what happens if you and your spouse have separated but not yet gotten divorced, as the Canadian newspaper The Globe and Mail discusses in "A warning for couples who have split but not divorced."
The laws in Canada and the U.S. are mostly the same in this area.
The law will not assume you do not want a spouse from whom you have separated, to not inherit under your estate plan.
Why? Until a divorce is finalized, you and your spouse can always get back together and courts cannot divine what you intended.
The solution to this problem is to see an estate planning attorney, when you separate from your spouse.
You need to do this before a divorce is finalized, so the attorney can assist you in creating an estate plan that makes your wishes clear.
Reference: The Globe and Mail (Sep. 12, 2017) "A warning for couples who have split but not divorced."