It might not make as much money as live service but it might work like halo cars for the auto industry, giving them lots of press and attention and higher status as a game developer.
I think there is so much potential for a HL3. For example, messing with more recent discoveries such as the Higgs Boson to try to explain why stuff from another universe managed to be compatible with our universe, and have compatible DNA. That in itself would make for an intriguing plot.
