The ideas of Rubinius X will be added to Rubinius 3.0 over time, see the following articles for more info:

http://rubini.us/2014/11/10/rubinius-3-0-part-1-the-rubinius...

http://rubini.us/2014/11/11/rubinius-3-0-part-2-the-process/

http://rubini.us/2014/11/12/rubinius-3-0-part-3-the-instruct...

http://rubini.us/2014/11/13/rubinius-3-0-part-4-the-system-a...

http://rubini.us/2014/11/14/rubinius-3-0-part-5-the-language...