According to J.J. Abrams the Portal and Half-Life movies are still in the works.
In a recent interview about the upcoming 10 Cloverfield Lane film, which he produced, spoke about the Valve projects. He went on to say:
"Not yet, but they're in development," he answered. "And we've got writers, and we're working on both those stories. But nothing that would be an exciting update."
The movies were first hinted at way back during DICE 2013. At the time, Gabe Newell and Abrams expressed that they would like to work together to make films and games in the future.
Since then nothing new about the projects has emerged or be announced. 10 Cloverfield lane director Dan Trachtenberg made a short film called Portal: No Escape, but this hasn’t been linked to the project.
Hopefully we will hear something at some point in the future as I’m sure many fans would love to see this happen.