I like Python (and Ruby) a ton, but they may find themselves legacy-stamped if they don't develop a good concurrency story quite soon.

No big deal to be ~50 times slower than native code in a single-thread, single-processor use case, but for a well-parallelizable problem on a multicore machine you end up being several multiples of ~50 times slower.

Google just gave up on trying to optimize Python (see Unladen Swallow project) and told the engineers to move on to something useful. I am not sure if the interanls are just to messed up too make it work or if resistance and denial on the part of "B"DFLs and the community is too strong.

But when javascript - JAVASCRIPT! - has a better server-side concurrecy pitch than your language, it is in big trouble