This will actually happen as J.J. Abrams and Gabe Newell were already talking about it, they finally concluded that they will make both a Portal and a Half-Life movie.
Gabe Newell confirmed that the movie is still being worked on in a Reddit AMA in 2017.
In 2011 the video game Portal 2 included a interactive trailer for J.J. Abrams movie "Super 8". The Player was able to investigate the train crash site from the movie in a real fantastic way.
During a press day for the home release of Super 8's 4K Blu-ray, Abrams confirmed the Portal movie's status to IGN. "We actually do have a script that's being written for the Portal movie now at [Warner Bros.]. We're really excited about the take and the pitch, so it feels like that thing's finally on the rails."
Krysty Wilson-Cairns said that early on in her career she pitched an adaptation of the Portal movie but was turned down. She says she's still haunted by the fact she didn't get to make the movie.