The statement implies a clear distinction begins to be made between the line of Seth and the line of Cain. The Lord will never allow His people to be wiped out from the earth. God's people are marked out here and throughout history by worship. Worship is central to life. Worship restores man in his ability to take dominion over the earth.
Worship is designed to restructure our thinking and reset our course along the lines of our calling.
The word which closes out chapter 4 is the great word of victory and hope. God restored those who would call upon His name and if that occurs, then all is sure to be well.