What's the canonical definition of end of the buddha sāsana?

I was under the impression that the end of buddha sāsana occurs when noble eight-fold path(and the dhamma practitioners) disappear form all the realms including Śuddhāvāsa where only anāgāmins live. This contradicts with Ghatikara sutta . It consists of a lord buddha's conversion with an anāgāmi brahma Ghatikara form Kashyapa buddha sāsana. That means at least anāgāmins and arahants from previous buddhas might still live in arupa brahma realms. Did anyone come across a canonical reference for end of buddha sāsana?