Your first point is utterly incorrect. Serious programmers use a lot of Perl and Python - Java lacks the dynamic features and huge back catalogue of readily available C, C++, etc libraries.

Any C or C++ library can be used within perl and Python (or even PHP) applications. You will find that Perl and Python have more than their fair share of serious programmers and major ecommerce and other systems continue to be built with both languages. Java is too slow, too complicated and too tightly linked with the huge collection of tools required to make any java programmer productive.

as for point 2 - Mono is plenty ready enough for any well designed C# or .NET application - only a very small number of bleeding edge MS development houses are making serious .Net deployments and most .Net applications are far from ready to market.

By the time that the majority of MS development shops are working on testing and QA of their .Net applications - testing their applications against Mono so that they can run on UNIX and Linux will be a no-brainer.

Your third point is partially true in that Java on Linux is now fairly mature while .Net still lacks the testing, deployment, community and documentation, but then Java is still behind Perl, Python and C/C++ in terms of maturity and mindshare of serious developers.

Also I am already using more applications written in any of c#, python or perl than Java. There are no killer desktop or server applications in Java.

Gnome and other open source projects are already providing useful desktop tools and I already depend on a great deal of perl and python tools on the server with no Java in sight.