Bunch of newbs and their premature ejaculation issues...
This is the 4th generation, and trust me when I say that selling current phone ahead of release is not worth the few dollars you make in between.
Everyone knows about the upcoming release, it's not like if they are considering buying your 3GS now, and they would change their mind in a month because 4G has been released.
The newb with "ejactualtion issues" would be the one that doesn't consider competition w/ every other iPhone user flooding eBay and CL with their old phones after buying the new one.
Also, some of us have other phones to fall back on. I have an iPhone from work that I will use after selling mine.