China had the final say since the end of 18th century. Even THIS (14th) Dalai Lama was approved by Chinese central government. One of the Dalai Lamas was a Mongolian from the royal family which was ruling Tibet.
I've been to Tibet. Lhasa is quite different from other Chinese cities. "Tibetans are a minority in the most of Tibet - certainly in the larger towns and cities", this is a lie. I wonder why many people believe this lie. It seems that propaganda of Chinese Communism Party is not so powerful. Another big lie about Tibet is that Chinese killed 3 million Tibetans. Dalai Lama repeated this number many times a couple of years ago. If I say 600 million Americans are killed, anybody believes this number? I have great sympathy for Tibetans and I know Communism Party is a big time liar, but we can not use a "smaller" lie to fight against the big time liar. I've to doubt Dalai Lama's integrity. He is a monk, not a politician.
I do not think the "disappearance" of Tibet culture is a big deal. Northern nomadic tribes invaded China many times, finally most of them lost their identities, and their culture mixed into Chines culture. Today, Western culture is the main stream, the pure tradition Chinese culture is also "disappearing".