Since the release of 0.63 experimental I have not come across wolves (or any other animal than chickens actually) in the world. And the last week on stress test #31 I have been travelling back and forth in wolf territory, day and night, to try and find wolves. Nothing. So either the animals are not spawning at all or the spawn is so rare that it is basically irrelevant. In 0.62 never dared venture into wolf territory without a lot of firepower, now I'm running about anywhere without a care in the world other than exposing myself to homicidal players...
Same goes for cows and deer, not seen them once in 0.63 and neither has anyone I've talked with, except for early stress test builds offline.