I think this will actually be a good thing. When I first came to Seraph there was usually 2500+ people online, and could usually find or put together a party fairly quick. Nowadays though, you're lucky to see 1000 people on at any time, and parties/events/missions take quite a bit longer to fill (I shouted once for 3 hours for a Nyzul Boss run).
So what this is going to do is just make it feel like it used to be. Areas will be livelier, parties can be found/made with a lot more ease, and while most of us are into endgame and all that, this will be a huge thing for new players, and make their time in FFXI that much more enjoyable.
As one person pointed out, it's kind of like getting a clean slate to start over, except you can still have all your friends with you.
And most importantly, you now have thousands more people who might just end up as your next friend in this game! I just don't see how this can be a bad thing. I am looking forward to being a part of the Bismarck population, and can only hope I can actually find more pet job enthusiasts such as myself!