With time and good dietary management it is possible to regain some insulin sensitivity. In Type 2 Diabetes the problem is not with the insulin itself it is with the insulin resistance of the cells/tissues.
In my opinion, even if a person with T2 reaches and maintains non Diabetic HbA1c numbers they are still insulin resistant and still have T2. There is no cure. People can (and have) improved their insulin sensitivity to the point that they are able to raise the amount of carbohydrates in their diet but a return to 'normal' diet would result in worsening blood glucose levels.