Valve is ready to gamble.
After being hesitant for years to suscept Valve's IPs to the consequences of video-game based films, Gabe Newell has decided to give it a chance. At DICE 2013, he said the following:
We reached the point that we decided to do more than talk.
The "we" he refers to is none other than J. J. Abrams, the man behind award-winning films such as Cloverfield and Super 8. Looking at his history of work, he's probably the most qualified person to bring Half-Life and Portal to life. Newell has taken notice to this, and has already made the first moves to collaborate with Abrams on films for both franchises.
It's a scary thought when you consider the ratio of failure for games that turn to the big screen, but there's also a huge opportunity if executed correctly. There's clearly something that has gone on between Abrams and Newell that has instilled confidence, and if Newell feels that it's right t then gamers can't do much but bite their fingernails.
The films are only in the earliest stages of concept, so it's going to be a few years before we see anything come of this. The question will be if it'll come out before Half-Life 3 does. At this rate, the film stands a better chance of winning the race.