Big bang 3rd of december? Does this screenshot seem legit?

They wouldn't have an update immediately follow a 9 hour maintenance. It wouldn't make sense. If anything, this maintenance pushes back the date of the big bang patch.

They wouldn't have the most anticipated update ever follow a 9 hour maintenance a week later?

I bet you they would. Why wouldn't they? It's not like someone is going to complain "oh you are putting in Big Bang, but since you had a 9 hour maintenance when I wasn't playing anyways, I'm going to whine because I feel like it."