omg, I'm going to have a boss! I'll be working at Atlassian. Lots of stuff to still do in the future to reach our (and my) goals. And now we're going to have a lot more fuel for our engines to get there.
I obviously have no idea how Trello is structured and whether Michael has any real ownership or not, given its unique history, but in the case of most SaaS founders, when their golden handcuffs expire, they call in rich, because duh, why wouldn't they? Especially after watching the bureaucracy at the acquirer kill their baby.