Someone said it would take a significantly heavier launch vehicle in '09.
Not sure who. I doubt that would be a show stopper since there's little development and testing costs. They might want to give it a microscope that can see single cell fossils (duh!), and a telescope like Tom is always complaining about. Maybe tweak the heat shield if they learned anything from Oppy's inspection. No doubt they'd try to upgrade some capabilities but it is essentially a ready to go robot.