When the Earth Warms, Won't the Areas That We Lose

When the Earth warms, won't the areas that we lose to agriculture (like the U.S. Midwest) just be replaced by new areas that are now too cold for farming (like Northern Canada) ?

A) No. The areas that will warm will still be too cold to farm.
B) Yes. There really won't be any problems for agriculture once the Earth warms.
C) Maybe. There is more to farming than just climate and more needs to be known about the soil characteristics in those areas.
D) No. There aren't enough people in those areas to farm the land.
E) Yes. The amount of land that we gain will exactly replace the amount that we lose.