We don't have a definite answer to this question. The Japanese people have been through so much over the decades with fortitude, competition, solidarity, and unity among their people.
They also have to deal with depression, anxiety, loss of life and grief. Picking up the pieces from Post Traumatic Stress includes more than just mental fortitude and emotional equilibrium.
The land is desecrated from ocean tsunami, broken glass, and nuclear radiation fallout. Individuals will succumb to disease and apathy. It will take an international effort to clean up and rebuild.
The question is how and where? They cannot reconstruct on the same location by the shore and fault lines. A totally new outlook on life and harmony with nature will be the only way.
Time? How long? I cannot predict.