Of Course Wii will reach 50% this year, and will be quite above it when 2010 rolls in, by the end of the generation Wii could be above 60%. Nintendo will increase production once again for holiday period.
About your arguments:
You list big PS3 games, but you forget that the best selling games this gen. Will be on Nintendo Console: Wii Fit will outsell the PS3, Mario Kart sells like crazy, Wii Sports Resort will sell more then any game you have listed.
Japan, well Wii still dominates in that region, and yeah PS3 looks good for 2009 but can it really outsell the Wii for more then 10-15 weeks this year? Wii Sports Resort and Monster Hunter III are coming to the Wii , and those titles will be big in Japan.
Price: Cheap 360 sells a lot but still does not outsell the Wii, In the UK Pro version is cheaper then the Wii, and Wii stays on top. Price is not everything 99$ Gamecube did not suddenly start outselling the PS2, and this same wont happen with HD Twins.
