Would they need BTC? With 1.3 billion potential users wouldn't that be enough?
I would say there will always be some kind of relationship between national cryptocoins and btc. China (and most likely also other countries) will surely control miners and it's even question if algorithms will be compatible or not. So it will influence the btc but on a smaller scale.
I also think BTC will always be interconnected with all othe cryptos.
And not only China mostly all countries have possibility of having their own coin, and they all will be connected.
Bitcoin will always be there.