I am somewhat concerned by this since I have a large order of singles that still have not been shipped to me. Basically it means in order to stay competitive the investment I had secured needed to be 50% larger then what I got. My order is not scheduled to arrive until late July or early August and that is only 2-3 months from when the ASIC product would come out.
With all things staying even that is like $100 a month per single without any kind of power costs taken into account. So while I guess you would maybe pay off half of the single if you did nothing but sell the coins to pay yourself back, you would still be $300 per single short of replacing them with the ASIC product.
Of course that is also if they ship in October, the price and difficulty stay the same, and there is a reasonable turn around time from when you order and turn off the singles and ship them to BFL before you get your replacement hardware. It would be pretty horrible if you order, and then turn off the singles/mini rigs you have to only wait 2 months or more to get the new ASIC.
I think if you could secure your order with a credit card they would ship you the entire shipment of ASIC products and once you get them you could send back the singles/rigs for a refund to the card. Maybe I missed it but it seems this trade in policy seems more clunky then it should be.
Personally I wouldn't be too worried. Most likely they will ship ASICs much later than October, and you can use your singles until they are ready to ship your ASIC order (at least that's what they have said). And if you don't have the $ to exchange all your singles, you shouldn't have any trouble selling some of your singles to raise cash. The singles should hold their value since they are good for a $599 credit toward the purchase of ASIC equipment.
