I can knock out a good website in an hour in PHP, and an excellent one in a day or two. Its performance characteristics are well-known and understood, so I can make it scale pretty much indefinitely. Every developer we'd want to hire knows it, and every system we'd integrate with has a wrapper library written in it. I am trapped by the convenience of PHP in a language that is losing its suitability for the task.
What's happened with PHP is that we've become too convenient and lazy. Everybody uses it – why change? It's an evil spiral I don't want to go down with. "PHP needs to die" is perhaps a bit harsh, but I definitely think it shouldn't be the first choice of web server language when beginners grow out of HTML and CSS (it is actually very much a de facto language). In a perfect world, web hosts (even shared hosting providers) would offer Ruby and Python out-of-the-box without any addon fees.
I want a language that assumes everything I will be building is an MVC web app, and builds that right into the core language, not just a library.
To become the Number One Web Language, it has to look on what made PHP big: drop in functionality, straight forward documentation, simple hosting, and a not too steep learning curve.