This occasionally happens as does the inverse - a couple starting out in mediation and finding it necessary to litigate.
If both spouses opt to settle their divorce amicably and without attorneys and litigation, then the couple would need to inform their respective counsel that this is their decision, the attorney(s) would "sub" out of the case, and the couple would proceed with their court case each being in "pro per."
A qualified family law mediator would be hired to mediate and settle the remaining issues in the case, and help the couple close out their divorce case.