mhm, I suppose they can always try to get the cold resistant in with an autoflowering strain so it doesn't go back into vegging. An autoflowering strain that can withstand temperatures in the negatives would be awesome......Its not so much the problem of the cold its the fact that the short days will send the plant into flower. So even if it was cold resistant it would still have to spend the majority of its life in summer to be able to harvest in winter otherwise the plant would start to flower in the winter and if not fully done once the summer days roll back around it may try to reveg on you.
It wouldn't take that long...autoflower would be the least of your worries, the only other plants that are alive during the winter, are carniforous trees, at least where i am. so unless you pliced pine tree genes, your gonne need more like 30 thousand years