Considering Rize of Zilart came with the 'original' story, and that Rize of Zilart ties directly into it... I'd say that Shadow Lord isn't the final boss.

Plus, when you consider the date the OP posted this thread you have to consider what completed expansions are available; at this point in time to complete the game in terms of storyline you would have to complete all the currently complete expansions (original, RoZ, CoP, ToAU, the three mini-stories).

I'm not even sure why you're trying to argue this Necro, I doubt you could even give a flying smurf (something I notice in this forum with quite a few people). If the OP wants to complete FFXI, then I'm sure he'd want to complete expansions that are out, and by the time he would complete them then WoTG would be finished and I'm sure he'd want to complete that to get the most out of the story/experience.