According to Valve’s Chet Faliszek, the developer could build another part in the series.
Faliszek was asked by Eurogamer.net if there will be a Left for Dead 3:
“A 3? You know, some time down the road,” he theorised, “Like anything, I would say that to all of our games. So that’s not a promise of when or where. I really love working on that series. It’s one of my favourite series. It’s just so much fun with the characters and the world. I love zombies and I love horror. So, yeah.”