I think you are talking about the cultrure reveloution, which was disaster for the whole country not only for Tibet. But It's already in histroy and it's over. The fact is tibetans are chinese people, this is China's problem. And we are solving this problem now.
Who told you most of Tibetans are living in exile.
As the newly finished rail way, the development in Tibet will catch up with the rest of china. The small number of Tibetans who misled by DL will come back to China.