It looks like there is a new Portal game on the way, but probably not the one you were expecting. And much to everyone's disappointment, it's not Portal 3.
Bridge Constructor Portal will be a completely standalone title and "fully embraces" the Portal license, with all manner of fiendish conundrums and an "exciting new game experience". My absolute dream would be for Valve to acknowledge this game as canon in the Portal universe and slips in some additional tidbits on Aperture Science.
Rumours circulated overnight that a new Portal title being revealed at The Game Awards. While everyone is waiting for Valve to release another sequel, Headup Games has announced 'Bridge Constructor Portal'.
The game will launch in two weeks, starting with the PC versions (Windows, Mac, and Linux) and Android/iOS devices on December 20. "The console versions will follow in early 2018". Though which consoles exactly weren't specifically stated, the video shows logos for Xbox One, PlayStation 4, and Nintendo Switch.
You'll need to combine your physical construction skills with your knowledge of the laws of physics and portals to overcome devious test chambers. This will be the first Portal-related game that has been released for mobile platforms.
You do get a feel for how everything will work though, with the game featuring portals (obviously), turrets, and the voice of Ellen McLain as GLaDOS.