If the Shar'i talaq was conducted in the correct way, with all the fiqhi conditions met, then the wife's 'iddah period will be 3 menstrual cycles.
After this, the wife will no longer be mahram to the husband.
Of course, this would alsodepend on what type of divorce was perfomed. If it is a Ba'in (irrevocable) divorce, then the wife becomes non-mahram once the divorce is conducted.
And Allah knows best.