The end of the arc is usually defined as the last chapter that the crew is on the island. For a recent example, Chapter 1057 is considered the last chapter of the Wano arc. The Egghead arc started with Chapter 1058. At the time of this question's creation the last official release of the series is Chapter 1107, with the arc currently being 50 chapters long.

Guesses should be specific chapters, not ranges.

Will be resolved upon the final chapter's release or extended if need be.