If a husband and wife have Wills, when one spouse dies does the living spouse's Will become null and void?

The answer to this question should be "no."  I don't practice law in Georgia, but I would be very surprised if Georgia had a law that declared a spouse's will null and void if the other spouse passes away.  On the other hand, the surviving spouse's will may be ineffective - depending on how it was written.

Most wills provide for contingent or successor beneficiaries.  This means that the will leaves everything to the spouse unless the spouse dies first.  If the spouse dies first, the will usually names the people who will then inherit.  If those successor beneficiaries are still appropriate, there is no need to change the surviving spouse's will.  If those successor beneficiaries are no longer appropriate, then I suggest changing the will.

This whole scenario is complicated by second and third marriages.  If the husband and wife have been married before, and especially if they have children from prior marriages, I suggest the surviving spouse consult a life or estate planning attorney.  Many attorneys do not charge to review an existing plan and can explain what will happen with the existing will.