I don't think this is a true concern. When I took the AP class we used Java 1.4. I'm sure you know how big the differences are between Java 1.4 and Java 1.7. The AP course is about the fundamentals of computer science, the language doesn't matter--it never touched Generics or Ant or anything a modern Java dev needs. But moving to Python allows for alternative curricula that's either pre-requisite or concurrent with the AP class that also uses Python and its abilities and easy-to-get libraries, like PyGame or Flask, to attract people into the field with shiny things.