Chinese won't rise as the most international language on Earth at least for the coming few decades.

Let's see, can you write computer programs in Chinese?

Would some of the chinese parents in Malaysia or in some other countries start to teach their children Mandarin of which they won't teach if not for the language's future usefulness? (Here I assume learning one's own mother tongue is not for any other reasons but for the cause of our color skin)

Mandarin is and would be an important language, but it should not 'take over' the role of English as the most international language, at least not before those who are in the generations to be able to see this thread die.

A good way to improve spoken English may be to improve written English at the first place. From certain perspectives, writing English is much easier than speaking English.

You'll need more than just basic grammar knowledge to speak decent English. (You don't really need good grammar if you're going to speak lah-lah-lah English)

The problem with people who are not courageous to speak English to other people may just be that they're afraid of being looked at with queer eyes telling them that they're not saying good English. If you could get your grammar right, what fear should you have?