Well, the good thing is, space is full of... empty space. Unlike games such as Skyrim or whatever, you don't have to load and render a truckton of scenery models every 10 meters. It should be fairly possible to stream planets and ships continuously if the engine pipeline isn't a turd. There was a dev diary about this in which they explained that everything in the gameworld is "defined as containers." This pretty much means - for example - a container inside only gets loaded when you are inside of it as well. If you fly your cool space ship in space, the game will load distant planets / backdrops as well as other ships flying around, but not load the interior of the other ships or space stations, as you are not in their "container",... Anyway. Even Second Life does similar things since around 2003, just that it tries to load the full cell / grid in which you are, which in return is devastating for the game performance. No idea if anything about it changed by now, but the last time I checked it out, even with high speed internet it took a long time to load all the graphic objects. Limiting the traffic with that container system could actually work quite good, I'd say.
Not sure if the CryEngine was the best choice for that, though. Well, we'll probably see some day in the future...
/Edit: With all the fuzz about that game since a while now, it almost makes me feel like people *want* this to go down.