Yes, the will is valid. However in most cases a the old will can be revoked and a new will can be made at anytime. Also, a spouse may have certain rights of election that may trump the terms of a will that does not provide for the spouse. best to discuss the particulars of the situation with an attorney that specializes in estate planning.
The information that I am providing is general information based on my understanding of your question. You cannot and should not rely on this general advice in making legal decisions. There may be important information that you did not include in your question that could drastically change the advice an attorney that was fully informed would give you. I am not your attorney. My response does not create an attorney client relationship.
To be safe, I would suggest that he have an attorney re-draft a will adjusting for the fact that he is now divorced. Signing an antenuptial agreement is another issue he should be concerned with as well.
Disclaimer: This email message in no way creates an attorney client relationship between Majeski Law, LLC and the recipient. Responses are general in nature and do not constitute legal advice. You should consult a lawyer regarding any specific legal matter.