I also agree it's a good decision by Mark. Either he knows RedBull is going to decline with 2014 rules, or it's just the whole situation with Vettel is getting over his head, second of which is more likely one I guess. You could argue that Vettel's got the better of him, which might be true, still though you never know if new rules could suit Mark better.
Regardless of that he's 36 and it's the perfect time to make the switch in his age and with Porsche just making the return. He will be very respected and noticed among the new community, which he was once a part of.
What will Kimi do now, what will Iceman do now is the wonder. What will Torro Rossos do. This is going to be a brilliant couple of races ahead of us.