Update: A statement released by Official Nintendo Magazine reads:
The details printed in Official Nintendo Magazine 21 regarding Mario Kart
Wii were healthy speculation on our part and are in no way an official announcement from Nintendo.
"We are sorry if we have mislead anyone. We do not set out to mislead our readers. ONM apologises profusely for any misunderstandings that this has caused."
Update ends
Original story: As Reggie told a crowd of journalists at E3 earlier this year to "wait and see" how many players would be on the course at once in the new game, a trailer behind him clearly showed 12 karts lined up on the starting grid, as NGamer rightly pointed out in this huge preview.
Despite no further announcements having come from Nintendo, UK Official Nintendo Magazine says the online battle mode will allow for 16 players.