Well that was before they started giving dungeons a decent storyline (Tam-Tara HM for example). I would honestly be disappointed if they went with a "and then another siren comes along and causes more strife because why the heck not?" also, Pharos Sirius itself is a straight line from point A to B. There may be some extra rooms here and there, but the lighthouse itself is has no alternate routes to take to get to the top.