At the time of writing, 2009's Left 4 Dead 2 has more active players on Steam right now than Fall Guys, if you can believe it. There are two good reasons why Valve's co-op zombie shooter is having a resurgence: for one, it just got its first major update in years. Made primarily by members of the Left 4 Dead 2 community, the update packs in a ton of new content, and in recognition of that, Valve's also made Left 4 Dead 2 free-to-play all weekend.
Along with being free all weekend, Valve's slashed Left 4 Dead 2's price on PC, Mac, and Linux down to $1.99 if you somehow don't already have it collecting digital dust in your Steam library. With the addition of The Last Stand update, which includes a few dozen new maps, buyers are also getting more for their money than they would have a few weeks ago.
Centered on the new The Last Stand campaign, a fleshed-out story built around the old lighthouse Survival mode mission of the same name, the update Left 4 Dead 2 just got also includes a laundry list of bug fixes and improvements. This weekend's boom in interest may fade away quickly, but the update should keep Left 4 Dead 2's active community happy for years to come.
Unfortunately, fans who want Valve to revisit the series with a sequel shouldn't let this update get their hopes up. The recent release of Geoff Keighley's Final Hours report on the development of Half-Life: Alyx revealed that there was an open-world Left 4 Dead 3 project in the works at Valve in 2013, but it was abandoned at the time due to the limitations of the in-development Source 2 engine.
Then again, Source 2 has been around for a while now—Alyx, Dota 2, and the spin-offs Artifact and Underlords all use it—and the warm reception to Half-Life's return seems to have given parts of Valve a taste for making shooters again. If Left 4 Dead 2 stays active, maybe Valve will consider revisiting the series. Whether or not they do, now's your free-of-charge chance to check out why folks have stuck with Left 4 Dead for over a decade.