1) the foundation, that does all the outreach, education and magazines
2) The commercial part (the actually makes the pis)
3) R&D
but it might be only two.
Either way I assume only the commercial part will float, leaving the foundation as the majority shareholder. It has the advantage of giving the foundation a couple of hundred million, which should allow it to continue to do great things. (if you think about computer/electronics education, its basically pi and scratch. Arduino has kinda dropped the ball.)