Valve Software's Gabe Newell and headline-dwelling film producer/director J.J. Abrams have appears on stage together at the 2013 DICE Summit videogames event in Las Vegas, with a keynote speech that strongly hinted at a collaboration between the two for movies based on Valve games, and a game based on Bad Robot Productions property (via The Verge
Presumably speaking for his production company, Bad Robot, Abrams said on stage that "there's an idea for a game that we'd really like to work with Valve on," and Newell replied, "we're super excited about that and we also want to talk about making movies, either a Portal movie or a Half-Life movie."
Neither of the two men elaborated any further, but Newell did reveal that the on-stage discussion was a recapitulation of "a series of conversations" that the two men have already had with the intention of a collaborative project. Beyond the big tease, it is clear from the conversation on stage that the two are very appreciative of each other's work. At one point, Newell specifically called out one of his favorite scenes from Cloverfield, while Abrams said "I love the experience of playing your games" while complimenting that in Portal "there's this incredible mystery pulling you forward."
With commitments to both Star Wars and Star Trek films, we'd presume Abrams wouldn't be in a position to directly helm any other major film projects himself in the short term. So if we were to see a Portal or Half-life movie anytime soon, we expect he'd be producing.
As for a Bad Robot game from Valve, the production company has been behind an assortment of memorable film and tv franchises, but as far as we can tell, the licensing rights to most of the prominent ones --like Star Trek, Mission Impossible, Lost, and Fringe-- are all owned by major film studios. Perhaps its Cloverfield, or something new entirely?