I think if Mandatin started using pinyin or it could start dominating. The language itself isn't that much more difficult than other languages. You can get used to tones, too. The grammar is actually simpler than in English.

But the sheer number of characters to rote memorize makes it way too inefficient to learn for foreigners, and arguably even for natives, that I don't see it becoming a world language.

There's always the argument that pinyin isn't enough, that the characters are essentially useful. Which I think Vietnamese, which used to be based on the same writing system and is also tonal, proves wrong.

If you can't communicate with pinyin you can't communicate with the language, since it almost perfectly models the sounds.