Used iPhone 4 now or wait?

Ok so... basically I've been waiting 2 months to got the iPhone 4. Well last week, we went to the AT&T store to finally get the phone when the manager of the store told me I would NOT regret waiting as Apple has a very big meeting on Monday, one where they probably will announce the iPhone 4s. So I was fine waiting.. but then my dad comes home with a one month old iPhone 4 32 gig which is more than I was going to get for a cheap price from a friend. I guess its great cause its cheap and its 32 gigs and all but I take really good care of my things, I like things new and it has a small, hardly noticeable ding on the side (easily cover-able with a case). Well the only other upside is that then I could stay in my existing contract and not have to wait 2 years to get another phone so if one comes out later or early next year I could still get it. But I have a really hard time getting this phone when one might just appear two days from today. One much better. But then... It will be more expensive and I will have to renew my contract. But if I get the old one well.. its old and... I don't know. Any advice?