It seems that Sega was jumping the gun a bit.
Nintendo are publishing their first 'Cero D' rated Wii game in Japan - Zangeki no Reginleiv (formally known as Dynamic Slash). That is the equivalent of an M rating here. It isn't the first Wii game to get that rating (RE:4 and Dead Rising were rated Cero D too) but it is the first to actually be published by Nintendo.
It'll be interesting to see how much of a push Nintendo will give the game when/if they bring it over to the west.
In the meantime, Capcom's new titles seem to be getting some healthy advertising. Hopefully they get good sales as a result and then other 3rd parties understand what they have to do.