Oracle – Dev 2k and the future?

I have 4 years of rich experience in development of Oracle – Dev.2000, plsql and packages.
I want to know what I should learn now to keep me live in IT market. Though I want to learn Java, now-a-days, I have been hearing that Java will be replaced by C#.

I would like to know which IT tool is going to be dominating the future application development.