Speakers of ? language may not know the meaning of words in ? language on the wikis in ? language.
Who would benefit
Everybody who uses Wikipedia. Overcoming language barriers is a noble part of getting all people to have access to all knowledge.
The GoogleTrans gadget currently gives cursor hover translations to any user who loads it. It can do translations of selected text or translations of single words that the cursor hovers over (when the shift key is hit).
Make a version of the GoogleTrans gadget or a development from it available to all Wikipedia users, regardless of whether they load the current gadget or not.