I find it very easy to make friends in FFXI, just start chatting to people you're partying with. Chances are you'll find nice people with a good sense of humour. Regardless, if you start up on the Midgardsormr server, you'll have at least 5-6 friends from the start.

I don't think this game really has an end, there's always tons of stuff to do if you're looking for it, even after you reach Level 75, or maybe I should say especially after you reach Level 75. Square Enix are also releasing new material and events quite often.

You should definitely get the expansion packs right away. If you buy the 2008 version, you'll get all 4 expansion packs included. 15 pounds I think it was.

What happens to FFXI after FFXIV gets released is unknown. My best guess is that quite a few will stop playing while others will stay. Maybe they'll merge some servers to keep a high number of people on each server. I think FFXI will stick around for a long time, but you should decide whether you want to wait for FFXIV or try FFXI. Try the 2 week trial version!