Microsoft will have to start manufacturing blu-ray players for their xbox machines which they know is a huge market.
One thing to remember when beta-max died it died in the North America out in the rest of the world beta-max lived on and thrived in Japan thanks to SONY. So Microsoft could arrange a hit on Blu-Ray in the states in the PC market keeping HD-DVD alive long enough to thrive here in North America. Which would lead to a reverse situation in which HD-DVD lives on here in North America and it dies in Japan and Asia.
Remember hardware-wise HD-DVD is much cheaper and the most often cheapest wins in the states.