Well, perhaps not the world, but would it encourage more-re-use, less replication of basic code, or at least an uplift in what is considered basic code, more time advancing the application science and a greater encouragement to share, a more advanced base of understanding for new programmers, since the language could be taught ubiquitously and patterns of teaching would have emerged which were optimised for students learning etc etc? I think all of those things would make the programming world better and would probably have significant commercial benefit too.
This is definitely not a religious debate about which language is best, and is predicated on the notion of some super-being having designed the perfect language to start with, which was improbable, but it strikes me that if, from the beginning, there were only a single programming language we may be further along in terms of the evolution of the software industry and software science.
And although it is now impossible, if you buy some or all of these assertions is there an argument for standardising on a single language for the future so we can accelerate our collective progress rather than all of us re-inventing some part of the same wheel and consigning our children to the same fate?