Well, at some point you'll have to take your stand. But with the iMacs being just released there's going to be a higher demand/lower stock available which will mean ship times in the range of weeks, not days. I know someone who had ordered an iMac before the announced updates, got the free bump, and they still told her that it wouldn't ship until Oct. 29.
I gotta believe the ship time on your iMac is something similar... really what it comes down to is what have you got to lose by waiting? Only time... so if you aren't hurt by waiting, I would say wait. If you can't wait, that new iMac is one heck of a consolation prize.
