Its called PR Kirby, kind of like the DS being the third pillar, its entirely to cover their arses, if the DS had failed then they would have released a GBE fast, but now that its a success the GBE will be years off, if ever.
Same with the REV, if sales aren't as big as nintendo hopes, but it still seems to be purchased as a second system for most gamers then Ninty can say, look it did what we wanted it to do, it became a secondary system for many, but if sales are huge then you'll see the whole Secondary system talk be quietly thrown out the window.