According to the Washington Capitals official website, the Caps will be holding a press conference at 10:30 am Monday morning to make a "significant player-related announcement."

Watch it live here.

According to Capitals Insider, the presser is to announce the signing of Nicklas Backstrom to a multi-year contract extension: 
The Caps are expected to announce tomorrow morning that they have re-signed Nicklas Backstrom to a long-term extension, according to a source with knowledge of the situation.

I'm still working to get the particulars of the deal -- team officials are not answering their phones -- but Backstrom's salary is expected to be in the high $6 million per year range, I'm told.'s Pierre Lebrun reports the same:  
The Washington Capitals are set to announce a contract extension for star center Nicklas Backstrom, a source close to the situation told
This development, despite being a huge hit on the Captials salary cap, will tie the team's two best players, Backstom and Alex Ovechkin, together through their peak years for the Washington Capitals, giving them a dynamic first-line pairing for the forseeable future.

Backstrom, 22, had a career-high 101 points (33 goals, 68 assists) and a plus-37 rating in 82 regular-season games this season, his third in the NHL.