In Disneyland we were allowed to sit in the front of the monorail a couple of times last month (October 2010). So you can still have that experience there. My 4 year old loves to pretend he's the conductor. Perhaps if they eventually install new monorails in WDW in future years they might bring the riding up front experience back.
That is really the only way I see it coming back, the biggest difference is WDW Monorails are classified as Transportation while DL's are deemed an to be an attraction. I am sure that legally there is probably a pretty big difference there alone.
Remember the days when kids could sit in the cockpit of plane? (I sure do they were fun) Its unfortunate but we just live in a different world these days where sometimes people just want to do things to hurt us which is another reason to add to the list why these once fun things have become a thing of the past.