We're not saying you should send your congratulatory messages to the Facebook founder just yet. But according to this statement taken from a recent interview between Bill Gates and The Daily Mail, it's certainly a possibility:
He is friends with Facebook founder Mark Zuckerberg, 27, who has already pledged to give most of his fortune away. Gates lets slip that Zuckerberg may be engaged to Priscilla Chan, his long-term girlfriend: 'I didn't say to Mark, "Give me all your money!" He was predisposed to do it and he came to me seeking advice.

'His fiancée Priscilla thought about education and he gave money to Newark, New Jersey, and we did a co-grant so that some of our people who had some expertise in that field could help him out.
Right after the news broke, a rep for Gates explained to Business Insider that his statement may have been taken out of context:
We checked with Facebook's head of communications, Elliot Schrage, who suggested that Bill Gates was mistaken. "If [Mark is engaged, Bill Gates] knows something I don't know. Gates's communications guy just wrote to apologize for the misunderstanding."
Still, it wouldn't be that much of a stretch to assume that Mark Zuckerberg and his longtime girlfriend, Priscilla "Cilla" Chan, are making plans to tie the knot. The two have been dating since 2003, and, more importantly, and had listed themselves on Facebook as being "in a relationship" earlier this year.