Complex sentence: Maitreya will be the fifth Buddha of the present "kalpa" (aeon) and his arrival will occur after the teachings (dharma) of the Buddha are no longer practiced.
Split into simpler sentences: Maitreya will be the fifth Buddha of the present "kalpa" (aeon). It is foretold that his arrival will occur long after the teachings (dharma) of the current Buddha are no longer practiced.