The scenario that is most likely is:
The proportion of white-furred rabbits in the population declines.
As the average temperature increases and winter becomes shorter, the white-furred rabbits, which are better adapted to colder and snowy environments, may struggle to survive and reproduce compared to the brown-furred rabbits, which have a coloration that offers better camouflage in warmer environments with less snow. This could lead to a decline in the proportion of white-furred rabbits in the population.