Unfortunately yes, right now it's limited to Jython 2.2 (which is the internal version used). There are currently no plans to upgrade that version (mostly because it'd raise the size of PyDev a lot -- the jython jar is currently 1.5 MB, and the update would make it around 8 MB... The whole PyDev with Jython is right now 7 MB, so, it'd double the size just for that update).
I'd consider adding it only if it makes the startup of the PyDev editor much faster (right now, the first time you open a PyDev editor, it has a delay: that's Jython loading... I'm almost considering removing it because of that delay -- or at least making it optional, in which case it might be worth putting it in a separate plugin -- then, maybe it'd be worth updating the version, as users that don't want it don't need to get it).