Will JavaScript be the next big language?

I don't know if it will be the next big language, but I strongly believe there is a space for JS on the server side (actually ECMAScript). Why should web developers deal with two sets of languages? (JS on the client and whatever else on the server)

I am a long-time Java and C++ developer. More recently I've been actively developing in Flex, and I'm impressed with ActionScript (which now is ECMAScript). I for one would love to use ECMAScript on the server as well (today I use Java EE 5).