These verses prophesy the extent of the destruction. While it might seem like a positive image that a man would nourish a young cow and two sheep, and, therefore, people would eat butter and honey, that is not the purpose of the image. There is only one young cow, not a herd. There are only two sheep, not a flock.
While the people might drink milk, it is intended to be an image of all that remains. The honey is likely wild, and requires effort to supply. That this is intended to be an image of want is confirmed in the next verses where the land will be filled with briers and thorns instead of fields.
The final verse speaks of the cattle feeding in what once were cultivated fields. It is an image that Isaiah used before in his descriptions of the Assyrian invasion.