There are a few Portal mods that are in the works, including Portal 2: Desolation. But there’s one mod in particular that actually has a release date: Portal: Revolution.
The game is “a fan-made mod for Portal 2 which plays before the events of Portal 2 in the dead and decaying Aperture facility.” You are guided by the personality core known as Stirling, in the hopes that you’ll come across “a powerful device capable of restoring Aperture to its former glory.” Featuring 40 puzzles with “new test elements,” the playthrough is expected to last about eight hours. The difficulty “starts where Portal 2 stops” but “no puzzles require advanced tricky movement.”
Since the mod is using a custom version of CS:GO’s Source engine, this allows the small team of just seven members “to introduce many mechanics and improvements to the engine to create an experience which would be impossible in Portal 2.” And from the looks of it on the Steam store page, it looks like there will be a native Linux version of the mod.
See the Steam store page for more details.
Images credit of Second Face Software.