As Lionsfan mentioned the average number of people playing at a any given time has actually increased since the summer. I don't think FFXI is dying and until Square announces they are no longer supporting the game I don't think it will. Just look at the jp fan base. They've been playing for over two years strong and no serious signs of them leaving. The NA guys are just passing one year for the PC and the playstation guys have only been around for, what 6 months? This game won't "Die" for awhile, maybe 2 years with a few expansions.
Another point. I just bought EQ II when it came out. I was kinda bored with FFXI and bought into all the hype about FFXI being a time sink and the gilsellers are ruining the world, etc, etc. I'll tell you what, I only got through 14 lvls of EQ II before I realized I was being stupid. EQ II has time sinks too, all mmorpg's will or they won't last very long. Sure it has some cool differences like getting xp for qsts and some others, but it also was missing a lot of what brought me FFXI. EQ is a much darker game overall. Also, FFXI just seems to be a more fluid game overall. The economy of FFXI is really cool. Sure you can complain about gilsellers, but wait until you play a game with a very limited economy, like EQ. I'd take FFXI any day. I also like having good maps. EQ has always sucked in that department, I can't find anything, I hate that. I wasted a couple hours searching for something that should have been easy to find and the search ruined my night. I could go forever, but since i hate typing and would rather be playing right now, I'm out.
I guess the point of my rant was just that I'm not worried about EQ II or WoW or anything else killing FFXI. It will only die when a hypothetical FFXII comes out. late.
I'm a Lions fan, too. Detroit rocks.