3. China does not want Mandarin to become a Lingua Franca in anything.

Let's remember that China is a strongly nationalistic, protectionist, autocratic and most importantly successful country. Keeping Chinese for the Chinese give them enormous control leverage economically for their local market but also in entertainment, culture and more generally information.

I can see China simply promoting English in every field where it gives them a competitive advantage outside their border, like here in science.

Also there are technical and cultural difficulties for Mandarin to impose itself. Technically, Kanjis are a huge barrier to entry for learning, it takes years of personal investment to acquire basic literacy. You can't mix Chinese into English or English into Chinese very easily either. Culturally, probably by pragmatism because of the technical difficulties I mentioned, Chinese immigrants have not pushed for their language to the same level as South American for example.

So sure it is possible that this will changes, but that will take many decades.