What would be cool would be if iojs could become a feature feeder for nodejs. The only thing I can see that sucks from this forking is the talent split.
I don't think it will replace node. I think it will allow dev shops that are entrenched in legacy Java to start using node for new development or where it makes sense.
Having access to Java libs could be important for apps that already have a rich data model using hibernate or some other Java ORM.