That would freak'n rock the free world! Especially if it was lit and SAFE. That way you could ride back and forth at any time of day or night.
Unfortunately, the reality of this is highly unlikely. I have a friend who works for Caltrans and is involved with the bridge project, and when I asked him about this idea last year (why no west ped. span) he told me that in order to fit a path they would have to cantilever a path off one side of the west span - and it is not structurally feasable to do this (with the current design). Another bit of insider info regarding the bridge is that although intial projects say the bridge will be done by 2011, according to internal memos and stuff at Caltrans, they don't foresee it being complete until 2013!