In a recent interview with James Gosling at Sun’s World Wide Education and Research Conference in New York, Gosling was asked whether he considers the Java language under threat from any of the new-comer languages. Gosling replied that languages like PHP and Ruby (on Rails) are powerful at what they are designed to do, namely generate web pages, but are less suitable for implementing large enterprise systems.
Also of interest, C# was considered a threat to Java but no longer : “they’re hopelessly focused on one platform”.