Well, how long have Ultima Online and Everquest been around? A damn long time. FFXI has been as succesful as those, I think, so I believe it'd be around for quite some time now. There's still around 3-4 thousand people on a server most of the time, I don't think I've ever seen it go below 2 thousand, unless they've just done maintenance.

And the mega pack 2007 looks like a pretty good thing to get, if you're wanting to get into the game, nice and easy installation!

Just know, if you plan to play a hell of a lot, you'll get burnt out sooner or later (been there a few times). But just put the game down, go do something else for a couple of weeks, and see how you feel -- rather than deleting your character and swearing to never play again (been there a few times too >.<).

Anyways, enjoy!