If they're coming out with a Wii U and Mac version then that kind of supports the theory that they're going to add some sort of cross-console gaming. Otherwise I would think that there would be a shortage of players (or at least a HUGE difference) compared to the X1, PS4, and PC.
I would assume that by coming out on Mac that Mac would be on the same servers as PC. The only game I can remember playing on my Mac where I was segregated from the PC community was Borderlands 2. Other than that I always remember just being on the same servers as PC.
But I could see your point of there being a shortage of players on Wii U. Although you know my stance on Wii U being the only system worth owning!
I'm sure you could start one and see where it goes. Though the game isn't due until next christmas, so if you save a dollar a day starting today you will have enough to get a PS4 by the time it comes out. I am glad they are only focusing on these three platforms it means the game should be optimized for each platform making the experience as great as possible for everyone.
Could we sign a petition to have the game come out on current gen consoles?
Can we not, the more platforms they have to worry about, the longer it will take and the more resources they would need to divert from the current systems they are developing for. Personally I would rather that not happen. I would love to have them finish it as soon as they possibly can on the next gen systems...and those keyboard/mouse purists on PCs.