Isaiah 2:4 does not say God will bring world peace in the way people might imagine.
Isaiah speaks first of what is required of people--a strong faith in God and an obedience to His Law. When the people rise to this level of faith and obedience, Isaiah sees them bringing their differences to Zion where these differences are settled according to God's Law, not on a battlefield. When differences are settled in this manner, then "....they will hammer their swords into plowshares and their spears into pruning hooks. Nation will not lift up sword against nation, And never again will they learn war."
The first query we must have is, "When will people build a faith this great? When will their obedience to the Law of God be that strong?"