I would say that RO2 is likely to be heavily tied into Steam as are RO1 or Killing Floor. So you should be expecting fairly regular and sizeable updates to download automatically through steam.
These days if you want to play an up-to-date online shooter, broadband is simply a prerequisite in my opinion. I can see mods maybe being included on PC Gamer and eventually a Gold edition perhaps. But you are very unlikely to see them in their own stand alone published official expansion box any time soon really.