Ven the engine doesnt hasnt got anything to do with ported. The engine is the rendering of the graphics, physics, sound, animation and things like that. Like the unreal engine its used on all game machines (xbox ps3 pc). It might use the same engine but it also has been tweaked up.
E3 is only around the corner which they will release some more info, also the COD expo will be in a few months which they will release a lot more info.
I have faith in treyarch and believe they will have ranked dedicated servers. This is a company who listens to the PC community.
oh also still havent seen xbox on their advertising so DLC will be out the same time as everyone else.
Plus i think they might be hitting us with Elite 2.0 If so DLC will be cheaper for us for once