http://attackofthefanboy.com/news/paige-confirmed-wwe-2k15-roster-via-season-pass/

So in addition to the two Rivalries in the base game (Cena/Punk and HHH/Shawn) it looks like any other ones will be part of this season pass. Since we haven't seen how long each of these "stories" are I'll hold back on being a little bit wary of this, but the Attitude Era and Wrestlemania modes in the previous two years games were lengthy enough. Obviously this having the My Career mode of bringing up your own wrestler does mean there is other solo content though.

EDIT: And here's a more detailed article on the game overall from good old Bleacher

http://bleacherreport.com/articles/2224116-wwe-2k15-detailing-mycareer-mode-and-other-notable-improvements

Here is a full match list within those two rivalries that are included in the game. Warning, if you wanna go in fresh this could "spoil" that for you.

Seems like a good number to me and if it is like older games there will be plenty of other modes.

Like you though, I'll hold off on a season pass until I get the game and see what they plan to do for DLC.

@demoskinos posted the list of Rivalry matches 4 days ago in the Wrestling Thread.

Here's the list:

John Cena versus CM Punk Rivalry

• John Cena versus CM Punk for the WWE Championship (Money in the Bank 2011)
• John Cena versus Rey Mysterio for the WWE Championship (July 25th, 2011 edition of Raw)
• John Cena versus CM Punk for the WWE Championship (SummerSlam 2011)
• John Cena versus CM Punk (August 22, 2011 edition of Raw)
• John Cena versus Alberto Del Rio for the WWE Championship (Night of Champions 2011)
• CM Punk versus Triple H No DQ (Night of Champions 2011)
• John Cena versus Alberto Del Rio versus CM Punk – Hell in a Cell match for the WWE Championship (Hell in a Cell 2011)
• CM Punk versus Alberto Del Rio for the WWE Championship (Survivor Series 2011)
• CM Punk versus Big Show (July 16, 2012 edition of Raw)
• CM Punk versus John Cena for the WWE Championship (Raw 1000)
• CM Punk and John Cena versus Daniel Bryan and Big Show (August 13, 2012 edition of Raw]
• CM Punk versus John Cena versus Big Show for the WWE Championship (SummerSlam 2012)
• CM Punk versus John Cena for the WWE Championship (Night of Champions 2012)
• CM Punk versus Ryback – Hell in a Cell Match for the WWE Championship (Hell in a Cell 2012)
• CM Punk versus John Cena with Mick Foley as special enforcer (November 12, 2012 edition of Raw)
• John Cena versus CM Punk versus Ryback for the WWE Championship (Survivor Series 2012)
• CM Punk versus The Rock for the WWE Championship (Royal Rumble 2013)
• The Rock versus CM Punk for the WWE Championship (Elimination Chamber 2013)
• CM Punk versus John Cena (February 25, 2013 edition of Raw)

Triple H versus Shawn Michaels Rivalry

• Triple H versus Shawn Michaels Unsanctioned Street Fight (SummerSlam 2002)
• Kane versus Triple H – Casket Match (October 28, 2002 edition of Raw)
• Kane and Booker T versus Triple H and Chris Jericho (November 4, 2002 edition of Raw)
• Kane versus Chris Jericho versus Booker T versus RVD versus Shawn Michaels versus Triple H for the World Heavyweight Championship in The Elimination Chamber Survivor Series 2002)
• Rob Van Dam versus Shawn Michaels for the World Heavyweight Championship (November 25, 2002 edition of Raw)
• Triple H versus Rob Van Dam (December 2, 2002 edition of Raw)
• Shawn Michaels versus Triple H – Three Stages of Hell For the World Heavyweight Championship (Armageddon 2002)
• Shawn Michaels, Booker T and Kevin Nash versus Triple H, Ric Flair and Chris Jericho (Backlash 2003)
• Shawn Michaels versus Ric Flair (Bad Blood 2003)
• Shawn Michaels versus Batista (Armageddon 2003)
• Triple H versus Shawn Michaels for the World Heavyweight Championship – Last Man Standing Match (Royal Rumble 2004)
• Shawn Michaels versus Randy Orton (June 7, 2004 edition of Raw)
• Triple H versus Shawn Michaels for the World Heavyweight Championship -Hell in a Cell (Bad Blood 2004)