[VeejayRampay]

Python/Ruby/whatever will most likely get faster as access to tools like LLVM and the JVM itself is getting more common these days. You'll still get the HUGE bump in development times (due to the inherent expressiveness of the languages) and at least a good portion of the speed benefits you'd reap from Java itself.

[CmonDev]

"You'll still get the HUGE bump in development times (due to the inherent expressiveness of the languages)"

Not sure if that is true. Maybe for small typical web-projects or server-side scenarios that benefit from thin scripting layer (like at Google). If it is true though, then Haskell and OCAML/F# would be even better because you get expressiveness without loosing the obvious advantages of strong static type systems.

[VeejayRampay]

Those language are too cryptic for people to adopt them en masse.

There's a reason why Ruby/PHP/Python are so pervasive, 95% of people simply do NOT care about monads and poly-variadic fix-point combinators for mutual recursion.