Search the Java News forum for a lot of discussion on this. The short answer is that most people seem to agree that there are too many companies with an investment in Java for it to die with Sun (assuming Sun dies).
I feel confident that java will survive even if Sun dies. But I feel that even Sun will not die. After all it has tremendous good will in the developer community and is recognized as a good company. Certainly all that should count for something in the market.
Even Java is becoming superfluous. Java is the Dan Marino of software. Just as the former Dolphins quarterback, Java affected the world so much that history cannot be written without its mention. But nonetheless, neither Java nor Dan ever won the big one.
Dan Marino led Dolphins to Superbowl appearance in his rockie season. They lost. Dan Marino later told reporters that he want to play in superbowl the next morning when he waked up, but until retirement, he never got another chance. I remember he saying "you never know when you can get back to it". It is kind of sad. But I can't see a lot similarity between Java and Dan Marino, because Java still has chance? or never reach superbowl.