I am Broker/Owner of a real estate firm and can't disparage some of the responses because in essence people (I am referring to realtors) sometimes forget the difference between earning a living and doing the right thing by their clients. Hence, my desire to go out on my own.
That being said, I find myself straddling the fence a bit between the comments of Jmotrulia and Hagen in that as much as it is true there will always be a market for million dollar plus properties and Key Biscayne in particular is a unique place... It does not detract from the simple fact that not much is going on right now... One positive note about the island is that despite being next to ground zero of the condo boom it has fared "relatively" well compared to some other areas. It isn't to say the Key has in some way escaped the fallout. More importantly, I do agree that there will continue to be adjustment in price.
But, I have started to see some small deals pop-up on rental condos and noticed some good downward movement on interior lots on island as well.
It is quite certain that the more affluent buyer is not as much affected by the bursting of the real estate bubble as the not so affluent, but in any case, buyers are available. We, (listing agents) just have to work a little more and harder to sell our listings, but they sell.
Best of luck.