Apple's most recent display update was in March 2002 - with the relatively surprise introduction of the 23" Cinema HD Display at MacWorld Tokyo.
This newest display brought a 23" 1920x1200 pixel resolution display into their LCD product line. Now with 15", 17", 22" and 23" sizes.
The only hint about the 23" Display was a small mention in an EETimes article in January. This same EETimes article reported that Apple was working on other flat-planel technologies "including stereoscopic displays"... fueling the minds of Apple-fans.
Since that time, rumor-mongers have been speculating that the rest of Apple's LCD line would also be updated... but information has been relatively scarce.
Original rumors of an update to the rest of Apple's LCD line began in December from RailHeadDesign.com. At that time, the 15" display was to be dropped, and a new 19inch model introduced.
However, at the following expo (MWSF02), no new LCD's were introduced, but we did see the introduction of the 15" LCD iMac. Rising LCD prices throughout 2002 may have aborted the introduction of these rumored displays. These economic conditions also forced Apple to increase the price of the iMac during this time -- partially due to the rising cost of LCD Displays. With prices stabilizing later this year... there is hope that display upgrades will be seen sooner rather than later.
In April, Spymac echoed a similar report of a new 19" Apple LCD model... but with a MacWorld SanFrancisco 2003 target date. Recent aggressive rebates for current Apple LCD Displays may pave the way for future upgrades and price cuts.