Foxes like wolves cannot be completely domesticated.
In about 1000 generations it might be possible but not likely.
Humans have domesticated animals for many thousands of years and all the ones that were amenable have already been done.
Foxes are singular animals rather than pack animals. It is the pack mutual need that allowed the wolf to be domesticated. The wolf just transferred it's need for a pack from 4 footed and furry to 2 footed and relatively hairless.
A fox could be tamed down but since it doesn't have any need for community it would have no need to please. It likely would not be trainable.
A Russian breeding experiment produced completely domestic foxes within a very short period of time:
http://home.wlu.edu/~blackmerh/jsk/canid.htm
Sounds like every domestic cat I know.