Well they of course could make Acknex multi-platform but it'd have nearly just disadvantages (except for ports to the consoles). Introducing OpenGL as an alternative wouldn't just eat a lot of time to do (months of no engine improvement that Acknex imo cannot afford) but also would slow down the development from that point on (which they also cannot really afford imo). Then even if it were done there's next to no real advantage. The amount of Mac / Linux gamers is extremely small so there's no real gain at all...

Only for multiplayer hosts a Linux compatible client might be interesting but you could do that as sort of a standalone programm instead of porting the entire engine over to something that runs on Linux too...

Ports to the consoles of course might be interesting but I guess the question is if it's worth the effort / worth the costs. At least I see next to no games here that really would be worth porting to like the Xbox360 and with the main focus on newcomers in the game making business I don't see any real change in the near future. Plus this again would slow down the overall engine development which without additional manpower imo isn't really affordable...

Enjoy your meal
Toast