Greg Mankiw speculates that a world language will emerge, it will be either English or Chinese, and smart money says English will win. The interesting thing to me is that is it hard to become literate in either of the front-runners. Chinese is of course notorious for its lack of a phonetic alphabet, but English spelling is dreadful compared to say, German.
In my spare moments, I've worked out a whole system of phonetic English spelling. Imagine:
1. Dropping all silent and unpronounced double letters.
2. Dropping q (replace with kw) and x (replace with ks or z). Replace c with either k or s, and pronounce c like ch.
3. Standardizing vowels so that a single letter indicates a "short" vowel, and a double letter indicates a "long" vowel. Specifically:
The main problem for both Chinese and English, however, is that this is a classic coordination game. Who goes first? Em Ii gooing tuu start bloging with simplifiid speling, muc les riiting ortiklz? When you put it this way, I think Chinese has an edge over English in the race to be the world language. Chinese spelling is so bad that they might actually pay the switching cost of a well-crafted phonetic alphabet. English, in contrast, is bad but livable, so I wouldn't be surprised if English becomes a dead language before its spelling changes.