Disney just released their corporate earnings report. They missed most of their projections, and their outlook for the coming year was even more bleak. If they ever had a refurb in mind for Space Mountain, no doubt it has been postponed until late next year or 2010 and beyond. It's simply not in their budget to be doing anything to that attraction anymore, not if it cost $10 million and certainly not $100 million.
I would be shocked if they announced anything to the contrary.