I think you're right. The intersection of interested Ruby developers + with Java experience + knowledge of the Netbeans platform + and motivation/time to maintain the plugin seems vanishingly small.
The only thing is that Ruby is still growing, and so represents possible future revenue. But Oracle aims for short-term profitability now... which you have to admit, has worked out pretty well for them.
Taking a wider view, I love the work to make things better (such as at Xerox PARC), but it hasn't made money for those companies. Which is partly why Sun no longer has any say in Java, or in general research, or indeed in anything at all.
