As soon as you can talk Microsoft into open-sourcing the WP7 platform it will be done. The main reason Android was ported to the HD2 is because Android is open source and it made it possible.
Current phone: Samsung Captivate
Previously: HTC HD2, Google Nexus S, HTC Inspire 4G, Dell Streak, Blackberry 9000, T-Mobile G2, myTouch 4G, Samsung Focus, iPhone 3GS & 2G, Samsung Infuse, HTC Evo 4G, Samsung Captivate, Samsung Vibrant, Samsung Mesmerize, HTC Desire, Blackberry Torch. And that is just for 2011