The scenario that is most likely is:
The proportion of white-furred rabbits in the population declines.
As the average temperature increases and winters become shorter, the environmental conditions become less suitable for white-furred rabbits, which are better adapted to colder climates and snowy environments. Brown-furred rabbits, being more suited to warmer environments, may thrive and reproduce more effectively, leading to a decline in the proportion of white-furred rabbits in the population.