Near the end of this rather long interview with Ebon Upton, he mentions
the idea of having the Raspberry Pi boot directly to the Scratch screen
for smaller children or the Python prompt for older ones.

http://tuxradar.com/content/%EF%BB%BFinterview-eben-upton

His idea of having a minimal Linux hidden out of the way sounds a lot
like what Dan Ingalls had already done in his weather station PCs. So I
imagine it is a relatively easy product. If I understood correctly, he
wants a dual boot system so after a while a child can move on to a
regular Linux machine (by holding F1 during boot, for example). I
thought SD cards were now cheap enough that you could have two different
ones and then just swap them if you want a different system. At least
this is less abstract (and fitting in with the Pis retro theme, like how
people used the Alto and its removable disk packs).

In any case, it might be fun as a second step to go beyond that and have
a ScratchNOS built on top of the SqueakNOS project. This would only be
interesting if you could escape Scratch back into the full development
image, and then it would be important to change the name and disable the
uploading of projects as required by the Scratch license.

-- Jecel