Oracle has announced the discontinuation of Ruby support in the NetBeans IDE. The reason? First, to free resources for JDK 7 support; but second (and more significant) – hardly anyone was using it.
There is hardly a shortage of Ruby IDEs. Ones that come to mind are the Eclipse-based Aptana, JetBrains RubyMine, the Visual Studio based Ruby in Steel, and Embarcardero’s 3rd Rail. Further, some Ruby developers prefer to work without an IDE.
I also suspect that Ruby has not quite hit the mainstream in the way it seemed that it might a few years back. Its influence has been huge, but in practice many developers still fall back to PHP, Java and C#.