Last modified: 2011-03-13 18:05:37 UTC
Upon rollover, the reference would display as a tooltip (formatted still though, so probably would need js?) This would be in addition to jumping to the footnote upon click.
This is not really part of the job of the cite component, and as you say, needs javascript. This is already implemented at [[Wikipedia:Tools/Navigation popups]], and you can copy the js there to any other wiki if you want to use this feature somewhere other than the main wikis.