I don't think id would be successful with licensing in modern times without seriously changing their focus away from game development. Sure there is a great legacy of building games on id tech, but a modern game engine that is flexible enough to build a wide variety of game types and support different team sizes and platforms is difficult to build. For example, I seriously doubt idtech currently runs on any mobile platforms.
Most AAA game engines are good at making a game or a subset of games, and I imagine idtech 6 is great at making Doom, and by association pretty good at making first person shooters, but its not really possible to make a mobile match 3, 2D visual novel, or MOBA with it without heavily modifying C++ source. If you look at the HN discussion around Crytek open source, and peer into the source code, you'll have a good idea of the reality of many in house engines. In practice this is an advantage for AAA teams with strong engineers, because you can out compete people using licensed engines using features targeted for your game, but it makes it hard to do wide licenses to small teams that don't want to just make simple mods for your game.
I think the question for them is if it's worth it to license their engine for use by other titles in the genera it well fits, or if they feel that cuts too much in to their opportunity costs.
With the right partners (E.G. some company making an FPS based on a movie) the deal might work in their favor.
Most AAA game engines are good at making a game or a subset of games, and I imagine idtech 6 is great at making Doom, and by association pretty good at making first person shooters, but its not really possible to make a mobile match 3, 2D visual novel, or MOBA with it without heavily modifying C++ source. If you look at the HN discussion around Crytek open source, and peer into the source code, you'll have a good idea of the reality of many in house engines. In practice this is an advantage for AAA teams with strong engineers, because you can out compete people using licensed engines using features targeted for your game, but it makes it hard to do wide licenses to small teams that don't want to just make simple mods for your game.