Last year Wii achieved slightly over 50% marketshare for the year, this year so far it's been at 46.7% so it doesn't seem at all like it is making progress toward the 50% target....
I would disagree about Xbox360 and PS3 sales being flat for the next 6 months, they have big titles coming in the next 2 months that should help sales nicely...( but even if they stayed flat I don't think it would change things much).