Get the 5850 now, the price will not go down anytime soon, especially if Fermi is going to be priced higher (and it will be priced higher). This is not rocket science people, Nvidia has ALWAYS overpriced their video cards. This time, they will lose because ATI came out with a legit series this time and Nvidia is late late late...
If it's a noise issue, you could look into adding 5v/changing into 5v intake fans into your case. That way you can turn down the gfx card fan speeds to a more reasonable level while maintaining temps. If theres a positive pressure in your case, the hot air will be blown out the holes in the end of the card. The more positive pressure, the more goes out the back, obviously.
I know CF setups are far more prone to having problems than single GPUs, but you're saying theres no issues. I take it you're wanting a peace of mind of sorts? If thats the case, then go for it.
Of course, theres the whole having the newest tech, and everyone wants that lol.. If thats what this is about, and you can afford the price difference between selling and buying, then go for it.
If none of the above 3 applies to you, then I'm genuinely confused here.