It'll display it at whatever resolution the OS provides, but running at a decent FPS is another matter. I can run the game under Bootcamp at 2560x1440 with max settings at over 30fps, and to be honest I don't think it needs any more to look good. The max Bootcamp supports is 3840x2160, and the performance is not too good.
This is on an iMac Retina 5K with the i5 processor and M295X GPU.
Well, I'd certainly be happy running it 2560x1440, I'm sure it must look pretty good. Found this article too which proved interesting. http://arstechnica.com/apple/2014/10/the-retina-imac-and-its-5k-display-as-a-gaming-machine/
Bear in mind Alien Isolation is very kind on lower end hardware- putting something like Battlefield 4 might be a better test. My seven year old PC runs Alien Isolation with everything maxed, unlike B4 which is a pixellated flickbook.......
I'd be interested in seeing the 2 GPU options running ED but it seems that combination of owner isn't around yet.
FuZion.
I'm running a dual 680m config in my laptop - works nicely..
I made the jump & purchased an iMac 5k, i7, 295x & 16GB.
I have a solution to this problem - I use my iMac purely as a display for my uber-laptop. Full resolution, 60FPS. Looks gorgeous. The only downside is that I actually have to boot my iMac into OSX to enable Target Display Mode to make this happen.I think ED exposes the resolutions available, so at a guess I imagine it will be possible. But I'm not too sure about the iMacs GPU being up to the task, its a notebook part and looks a bit underpowered for higher resolution gaming.