According to one AppleInsider reader, Apple appears to have placed an End-of-Life (EOL) indicator on the current 17-inch Cinema Display:
I happen to call MicroCenter today to see if they had any 17" LCD monitors in stock and they notified me that they were completely sold out and that it is now a discontinued model. Apple will not be shipping any more to MicroCenter. The person stated that this only happens when Apple is coming out with something new to market. He did not know when or what, but the rumor that there is something else seems close at hand.
Cinema display revisions have been rumored for months but do not appear to be a priority for Apple, according to sources. Previous reports indicated that Apple would discontinue the 17" in favor of a revised line including 20, 23 and 30" Apple HD displays. The most recent information on the subject suggests that the revised display offerings would accompany the updates to the Power Mac G5 product-line due next month.
Update: Both of Apple's Major distributors, Ingram Micro and Tech Data, are said to have adequate supply of the 17" Apple Cinema Display, with hundreds on backorder.