PoD is Russian expansion eastwards, fending off and then conquering the lands of the Sibir and the like, is halted somewhere between 1380 and 1606. Assuming that Russia is thereafter unable or unwilling to expands eastwards much after that period of time, what becomes of that vast expanse of northern Asia? Would it become part of some Mongolian-ruled or -founded empire, be taken over by China, form its own nation-states, or just generally stay-unclaimed-by-everyone-except-the-natives land?