While there is no official confirmation anywhere, it appears that as of October 9, 2012, GameSpy has dropped online support of all Activision-published games for PS2.
Here is a complete list of all PS2 games affected, all of which I can confirm no longer connect to the GameSpy online servers. While DNAS still authenticates, the GameSpy servers of these games have been reconfigured to return an error message reading "Online play is no longer supported for this title." (or something similar to this):
Call of Duty: Finest Hour
Call of Duty 2: Big Red One (LAN supported)
Greg Hastings' Tournament Paintball Max'd (LAN supported)
The Hustle: Detroit Streets
Marvel: Ultimate Alliance
MTX: Mototrax (LAN supported)
Tony Hawk's Pro Skater 3 (LAN supported)
Tony Hawk's Pro Skater 4 (LAN supported)
Tony Hawk's Underground (LAN supported)
Tony Hawk's Underground 2
Tony Hawk's American Wasteland
World Series of Poker
X-Men Legends II: Rise of Apocalypse
The only exception is the Tony Hawk Series, as online play will still be supported through their regular online servers via CHC/Snipe's server at THPS.US, since they are configured to run through OpenSpy instead of GameSpy.
Theoretically, all of these discontinued titles could potentially be configured to run through OpenSpy as well (like Deer Hunter and Risk: Global Domination), but that project would require extensive packet capturing and troubleshooting.
It should be noted that this ONLY affects Activision-published PS2 games hosted by GameSpy, all other GameSpy games are still playable online, including the more populated games like 'Star Wars Battlefront II' and 'Battlefield 2: Modern Combat'.
The PS2 versions of 'Call of Duty 3' and 'World Series of Poker 2008: Battle for the Bracelets', both published by Activision, remain online as they are hosted by DemonWare.
As some of you may know, Glu Mobile Inc. acquired GameSpy Technology from IGN Entertainment on August 2, 2012.
Nearly eleven years after the release of the PS2's first online game, Tony Hawk's Pro Skater 3, could Activision's service contract with GameSpy have expired?Glu Mobile Inc. wrote:Glu Mobile Inc., a leading global developer and publisher of games for smartphone and tablet devices, announced that it has acquired GameSpy Technology from IGN Entertainment.
There will be no disruption in service to GameSpy’s current customers and contracts as a result of this acquisition by Glu.
Either way, OpenSpy's stock just went WAY up.