I'm sure everyone would like to see that, but I don't think it is realistic. Designing stages and environments takes up a lot more time and resources than cinematics do, and to fill up the entire disc would put the game in development for too long. Consider Super Mario Galaxy 2. It uses about 1.3GB as it is. Now, if they were to fill up the max space they have, which is 8.5GB if they go dual-layer, that's over six times as many levels as what the game contains currently. Assuming these stages are actually good, meaning crafted with the care and creativity of the existing levels, it'd have probably spent some eight years in development. That's just too long.
I think someone famous said something along the lines of "Games are never finished, only abandoned."