Well said, why not learn one framework and high level language and launch your own startup. In the beginning Facebook needed only php, twitter needed only ruby before moving to Java. Instagram is 98% python. When you begin to gather traction, you will employ the alpha geeks who use C, some of them are in Facebook and Twitter today. So just focus on building a product that succeeds with one or the only single backend language that you know in addition to some javascript and then use twitter bootstrap for design.

Why burn all that learning time to get a startup job, probably with reduced salaries and equity that might amount to zero if it fails. This is thesame risk you will face with your own startup but the difference is that the upside or equity is bigger if your startup takes off and you are doing it with the one language you know.