I think it depends a little on the future of the US. With its economy dwindling at the moment, if it doesn't recover and is greatly overtaken by China, the Chinese might get so much more of a cultural significance that some Chinese dialect becomes more sought after worldwide. Same might apply for some Indian language.
However, if the US rises back up, English may very likely stay important.
The international lingua franca changing isn't so damn far-fetched. It used to be Latin, then French, and now English -- perhaps, soon, Mandarin or Hindu.