PHP is unlikely to power the next start up. But I wouldn't be so cynical about it's success, especially in other segments of the web.
Lots of start-ups started with PHP (foursquare, groupon, facebook, etc, etc) because of the minimal cost and the convenience offered by popularity. If it works out and they get funding they can spend all that sweet cash on whatever they prefer.
Mobile apps and heavy REST services maybe not, but websites are still popular, and PHP is playing catch up for those services too.
I spent the start of 2008 migrating an agency off CodeIgniter - it definitely improved their projects afterwards (developer training helped too, but not as much as a well-designed framework did for code reuse).
What gets me is CodeIgniter is how I was writing PHP code back in 2003-2004, 4 years after picking up the language as a hobby. And people still think writing it like that is a good idea.
What else would they want people to think?
I guess it could all depend on your definition of 'anytime soon', but 5 years, 10 years from now, will PHP still drink 80% of the proverbial milkshake?