^ ^ Who would want to buy a locked Iphone 4? Only someone who has an ATnT connection. I cant answer that question, because Iphone 5 launch is still a very speculative date. If I have any news that It will be releasing this year, I would ask you to sell it. But since no such confirmed news is around the corner, I cant suggest anything im afraid =(
If you can find a seller who's offering a good price, sell it. If not, just hold on to it. 4.3 should be out end of this month, speculating it based on Verizon's Iphone launch (we will know tmw, Tuesday). So lets see how it goes...