It looks like Rufus and Lily are getting married ... as evidenced by the fifth episode of the new season being called "Rufus Getting Married." Yeah, we are good sleuths.
Added:

Gossip Girl Season 3 Episode 5 Quotes

Chuck: Look, I love you, but just because Nate liking Bree doesn't make her a piranha. And Serena liking Carter doesn't make him a prince.
Blair: Where are you going? I have tension!

Chuck: Look ... I may loathe the guy, but he didn't have to own up to anything. I bought him a ticket out of town. He risked a lot, knowing Bree would be there. He must really care about you.
Serena: The girl he proposed to was a Buckley.