Smash Brothers seems to be the exception. Iwata's pulled this trick twice, first at E3 2005--announcing work on a new Smash Bros was underway, that it would be a Revolution launch title with online, and then this year announcing a cross-platform Wii U/3DS title would be developed long before the development had started.
I'm not sure what the benefit of this is--with Kid Icarus delayed once, and no work due to start on a cross-platform Smash Bros until Kid Icarus is done, the next Smash game is years away. Brawl eventually came out in 2008, and had a massive development team--I shudder to think how long it'll take Sakurai to cook-up a 3DS/Wii U Smash Bros game.