New 21.5-inch Retina 4K models expected.
Upcoming Releases: PowerMacs, iMacs, iTunes?
All signs, however, are pointing towards the next few weeks as a final release time for pending Apple releases -- including PowerMacs, iMacs as well as the worldwide iTunes Music Store launch.
A European iTunes release in June has the most evidence available at this time. Apple had promised that the release of the Worldwide iTunes Music Store would come soon. Early sources reported that internal goals pegged an iTunes Europe launch in May 2004. Delays pushed the expected date to June 2004, according to our sources. Recent independent reports have placed the iTunes Europe launch specifically on June 15th, 2004.
A few other sources appear to confirm this date, and one suggests that iTunes Canada will also be part of the launch. Apple was previously known to be in negotiations with Canadian licensing agencies.
Apple last updated the iMac in November 2003 with the introduction of a 20" G4 iMac.
One reliable source had reported in May that the next iMac revision would sport a PowerPC G5 processor.
This ambitious report has seen some corroboration with a recent Appleinsider claim that resellers will no longer be receiving iMac G4 shipments, paving the way for an upcoming iMac G5.
The most anticipated release is that of the updated PowerMac G5s. Last updated at WWDC in June of 2003, the PowerMacs were promised to hit 3.0 GHz by [end of  summer or in 12 months (from June 2003)], but a lack of interim updates have spawned skepticism amongst the Mac faithful.
The introduction of 90nm PowerPC 970s in the January 2004 Xserves sparked some hope, but later reports indicated that cooling issues had delayed PowerMac updates.
The most consistent information available simply points to an all Dual PowerMac revision, recently Pictured in an unreleased service manual.
By current whispers, Wireless is reported to be "big" coming from Apple. The only related new technology that has been recently reported is Wireless Firewire which has recently been approved and new products (in general) based on this technology are expected by year's end.
I remain hesitant to even suggest something else as the frequency of various Tablet/iBox rumors seems to overwhelm more traditional (ie. realistic) reports... but some scattered whispers have suggested "something else" altogether... related to a hangable display/appliance. More details will be posted if/when available...