Last month I reported that the multiplayer servers for "Halo 2" PC edition would be shutting down this Friday, Feb. 15, 2013 as told by 343 Industries in their Halo Bulletin. Yesterday, Feb. 12, 2013 David Ellis, 343i's Spartan Ops Designer, posted on Twitter announcing that multiplayer support for "Halo 2" PC will be extended until June 2013.
Halo 2 PC support extended through June 2013 while we investigate further support options. Now go get those achievements.
Other than the mentioned investigation of support options, it's unclear as to if there were outside forces at play as well. Fans from all over, even fans that never played "Halo 2" PC, were posting and petitioning to keep the game alive for multiplayer support. While before the announcement 343i community manager Jessica Shea said that the average player population was peeking at 20 players over the course of the last few months of monitoring, that number slightly increased since the announcement that the game was being shutdown. Fans hate seeing a game become discontinued and that always makes players want to get one last game in before they can't play it anymore. Similar to the "Halo 3" event, aka The Great Journey, during the Super Bowl weekend.
While they investigate support options for the game, take this time and get those achievements that you never got and if your looking for players to join your quest, you can find them in one of the Halo communities posted here. Happy Hunting.