What usually happens is that Apple  by mrmacfixit Moderator -
3/6/12 4:35 AM  In Reply to: iMac regarding price by pinkzroxor
allows its stock of the old iMac to run down, just like what is
happening with the AppleTV right now.  Once announced, the new
item "usually" goes on sale immediately for around the same
price as the old one.  Places like MacMall, CDW or Best Buy, who
still have a stock of the old ones, will discount the older
models.  As to when the new iMac will be announced.......That's
anybody's guess