As for another language coming along. Will never happen. The language of the web must be community driven. And the community always disagrees. You know how long it's taken to get some seemingly basic features implemented? Forever. You get Adobe, Microsoft, Mozilla and more than a dozen other companies involved and each one wants something that disagrees with the rest.
And as for how it started? Netscape went to Brendan Eich and told him he had to write the language in 11 days. 11 days to implement the grammar, lexer, parser. Everything in 11 days. Then a bastardization version happened to be created by Microsoft, and bam. You have the language of the web.
JavaScript might not be the best language, but when used by experienced developers (no the overnight self-taught kind) it can be awesome. But regardless it's here to stay. So I wish people would stop bitching about how bad it is and focus on helping the developer community get better.