I wonder what he thinks the problem is, to which the languages of the world are competing solutions

Indeed, Todd. You could also ask in what sense the languages are in competition. The analogy with biological evolutionary phenomena seems highly dubious.

Further if language differentiation is all about the establishment of separate identity, then English can only become the only language for the world (according to the author's thesis) when everybody feels themselves to belong to the same group - or more likely, perhaps, the different identities will be asserted in different accents or small differences in grammar and vocabulary, along the lines of British versus American/Australian/Indian English.

It seems to me that the author has just not thought out how his position applies to lingua francas.