If the sense of smell and taste are lost for 6 months, will it return?

Depends on cause. Most common causes of loss of smell are nasal and sinus disease, uri, and head trauma. Taste loss can be due to dentures or oral disease and bell's palsy. Medication can alter your smell and taste. A complete head and neck examination with an endoscopic +/- radiologic look in your nose and nasopharynx will be needed.