"I believe the focus is on polishing up the Wii version, so I'm down for that as it means a better game in the end," said the community manager, who goes by the name of RubyEclipse in the forums. "If I hear and can pass on the exact reasons, I'll let you know."
The new target release date is June 2, but it might slip into the week after, which is when Grand Slam Tennis will be released.