Buy now or later

Hey guys,
My sis is looking into buying a convertible, I've suggested the Ford Mustang Convertible. When I told her the prices that what they're going for - she was really excited (speaking of which, why are they falling so badly? reliability issues?- I have a Lincoln LS, so I know about depreciation (and reliability but I love it and would buy again).
From what I can tell there isn't that much difference between the years 05-09(right?).
So I've been checking the prices on ebay and they seem to fluctuate around $~14K (buy it now price) w/ mileage around 25K for 2005-06. I've been putting many of the auctions on "watch this item" and many of them don't sell. What's even more confusing is when I price them on Edmunds TMV they come out at btwn $15-17K. So why no sales? Just wondering why there is this disconnect, any ideas?

I have heard about the new 2010 coming out soon, but when is that exactly? and I would imagine prices would fall even more on the earlier years, correct?
thxs

I think the 08's will be out of her price range. But will def go and see dealers in the next two weeks.
anybody know what the mustangs (06 v6 conv) are going for at dealer auctions (manhaeim) - I used a "independent dealer" when I bought my Lincoln LS - I got decent deal, however, it was a shady experience. It took about a month to get title and I'm not sure how he made money, all I paid was the auction price (+state tax) - which made me think he was pulling something. It may be simpler to just go to the dealer and pay a premium of 1K/