Source: 2012 US Open Cup format proposal calls for 64 teams, including all 16 US-based MLS clubs

and Dan nailed it...

CHICAGO (AP)—All 16 eligible Major League Soccer teams will compete in the U.S. Open Cup, which is expanding from 40 to 64 teams this year. The tournament will start May 15, with the second round May 22 and the MLS teams from the United States entering in the third round May 29, the U.S. Soccer Federation said Wednesday. MLS had entered eight teams in recent years, with six qualifying automatically and two emerging from play-in rounds. MLS teams must win five games in the single-elimination tournament to earn the title. The final will be Aug. 7 or 8.

Seattle will attempt to become the first team to win four years in a row.

All that matters is that this year it will truely be an "open" cup with the inclusion of NASL teams. I predict that the MN Stars will win it all. Come on you Stars!

2012 Lamar Hunt U.S. Open Cup Schedule:

April 29: Qualifying deadline
May 15: First Round
May 22: Second Round
May 29: Third Round
June 5: Fourth Round
June 26: Quarterfinals
July 10: Semifinals
Aug. 7 or 8: Final

Participating Professional Teams (32 total)

Major League Soccer (Division I – 16 teams): Chicago Fire, Chivas USA, Colorado Rapids, Columbus Crew, D.C. United, FC Dallas, Houston Dynamo, LA Galaxy, New England Revolution, New York Red Bulls, Philadelphia Union, Portland Timbers, Real Salt Lake, San Jose Earthquakes, Seattle Sounders FC, Sporting Kansas City.

North American Soccer League (Division II – 6 teams): Atlanta Silverbacks, Carolina RailHawks, Fort Lauderdale Strikers, NSC Minnesota Stars, San Antonio Scorpions, Tampa Bay Rowdies.

USL PRO (Division III – 10 teams): Charleston Battery, Charlotte Eagles, Dayton Dutch Lions, Harrisburg City Islanders, Los Angeles Blues, Orlando City, Pittsburgh Riverhounds, Richmond Kickers, Rochester Rhinos, Wilmington Hammerheads.

Distribution of Amateur-Level Places (32 total):
U.S. Adult Soccer Association Regional Qualifiers – 9 places: USASA regional qualifiers will increase their number of places in the tournament by one compared to 2011.

United Soccer Leagues Premier Development League – 16 places: The PDL will have the largest increase in representation among the amateur leagues since 2011, growing from nine slots.

National Premier Soccer League – 6.5 places: The NPSL is a national amateur league affiliated with the USASA. In previous years, its teams participated via USASA regional qualifying.

US Club Soccer – 0.5 place: U.S. Club Soccer is an organization member of U.S. Soccer.
Note: One team from the National Premier Soccer League will face a US Club Soccer representative for the final place in the tournament

http://www.nasl.com/index.php?id=3&newsid=1634

Here are the possible pairings for the third round of the tournament (all games May 29):

U.S. OPEN CUP THIRD ROUND
Houston Dynamo at either Laredo Heat or San Antonio Scorpions

Chicago Fire at Michigan Bucks or vs. Pittsburgh Riverhounds

Sporting Kansas City vs. KC Athletics or Orlando City SC

D.C. United at Richmond Kickers or vs. Aegan Hawks

Columbus Crew vs. Dayton Dutch Lions or Chicago Fire PDL

FC Dallas vs. Charlotte Eagles or El Paso Patriots

San Jose Earthquakes vs. Fresno Fire or Fort Lauderdale Strikers

Philadelphia Union vs. Brooklyn Italians or Rochester Rhinos

New England Revolution at Harrisburg City Islanders or vs. Long Island Rough Riders

New York Red Bulls at Charleston Battery or vs. Reading United

Chivas USA at Los Angeles Blues or vs. Ventura County Fusion

Los Angeles Galaxy at Carolina RailHawks or vs. PSA Elite

Colorado Rapids at Tampa Bay Rowdies or vs. Jacksonville United

Portland Timbers at Wilmington Hammerheads or vs. Cal FC

Seattle Sounders at Atlanta Silverbacks or vs. Georgia Revolution

Real Salt Lake at Minnesota Stars or vs. Des Moines Menace

Marc, you may want to start a new thread. The title of this one says 2012 and your article link is about 2013.