Decline and the ending of Buddhism
All Anagamis are born in one of the five Suddhavasa Brahma realms. There they will attain Arahanthship. Yes, they have a very long life span. The lowest realm 'Aviha' has a life span of 1000 Maha Kalpas. So they will see many Buddhas in the future before entering Parinibbana.

The text is talking about monks. That means the human world. Divine beings are not discussed here.