I read on a french blog that Cagni was leaving Apple to start a career in politics and had been pondering such a move for quite a time. He was renowned for his business skills but perceived by many EU employees as quite authoritative at times. In France, he is at least in part responsible for heated relations between Apple and some bloggers and possibly tense relations with 2 Apple Premium Resellers groups.
It was what was written on french Macbidouille.fr 's blog but I didn't see any confirmation of this info elsewhere.
Good luck to him under the new ultra-socialism in France.