The reason I say this is because a VC who merely breaks even on investments will eventually go out of business, so it would be a mistake to invest unless the expectation is that Docker might be a win for them.
Assuming Sequoia owns, say, 35%, then that comes to an expected acquisition price of about $1.15B for Sequoia to earn 10x their money back.
What are some hypothetical scenarios which end with Docker going public? What are some scenarios where a company would acquire Docker for north of $1B?
I'm not trying to imply anything about Docker with these questions. Personally, I love Docker. It's just fun to theorycraft.