Buddhism also says that an end to suffering in this lifetime is incredibly rare, something that qualifies you not just as an arahant but as a full Buddha. The claim that full Buddhahood is possible is obviously interesting - it implies that meaningful developments in enlightenment are very possible even after the conventional four stages of awakening - but obviously it's something that can only be explored by arahants who have completed these four stages. (And there's enough controversy about even the mere existence of modern arahatship, so the claim that it might at some time become common enough to make further progress feasible is even more speculative!)