"How about if one of our up and coming robotic explorers discovers water sources, or even past or present evidence of life on Mars?

I think a human mission will go into high gear in the short term."

Well, it depends on what you mean by water sources and evidence of life on Mars. We are pretty certain there is water ice at the Martian poles and there is some evidence that there was life on Mars. But say, we find a thermal springs which could have liquid water below a frozen surface or liquid water at surface which is rapidly boiling. Water which is easily accessible (minable) would probably increase the likeihood is a Manned mission happenning sooner. I doubt there will be such a discovery within 2-3 years- first we need to find areas which are promising, then successful get something down at the right location to confirm it. Then again, if we find a specific area which is promising for life, robitic sample return may be considered a quickier and cheaper way of getting the science return.
Now, if Odyessy gets evidence of widespread and abundant water sources in places where they is now thought to be pretty dry this could change things [though I imagine instead that the instruments will be suspected of somehow giving false reading- casting doubt on Lunar prospector findings and generally causing an uproar and confusion:]. I guess the best result from Odyessy would be finding a few areas which show high concentrations of water and within these areas evidence of really recent geothermal activity.