at least half of the world will become Baha'i

There is no reference in the writings stating that every single person will become Bahá’í, but at least half of them will. Rúhíyyih Khánum used to say that Shoghi Effendi was asked this question quite often by pilgrims. He would answer by saying that, in this Dispensation, the totality of the peoples of the world will not become Bahá’ís, but the majority will.

'Alí Nakhjavani, "Shoghi Effendi: The Range and Power of His Pen"