Apple is still working on a larger iMac with over a 30-inch display, but the development stage and potential release schedule for the all-in-one computer still remains largely unknown.
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As the rumors indicate, the actual size of the bigger iMac that Apple is working on is still unclear, but the display is surely going to be over 30 inches.
Surely???? The primary 'news' here is that it isn't a definate product. So how does the screen size fit into the guaranteed , 'surely' , status?
Very likely part of the problem here is Apple settling on a screen panel that fits they needs on cost and longevity. (e.g, if Apple is going to switch to tandem OLED for this .. for how many years at what price will it cost.). If > 30" costs too much for Apple, then it likely won't make the cut.
The only things in the 'surely' status is that it will be using a Apple SoC ( something in some Mn series) and it will have a large profit margin on it along with an Apple Logo somewhere. It would be > 24" since Apple already has one of those.
There are lots of assumptions that Apple could take a next gen XDR panel and wrap an iMac around that. But that is not a 'sure thing'. A relatively very expensive iMac may not shift economy of scale numbers for the XDR panels that much larger. Most of the discussions on these forums about an 'large screen iMac' are from folks looking for approximately the same legacy prices of the non-Pro version.
Pretty good chance that the Studio Display is substantively outselling the XDR at this point. If larger screen iMac was going to 'couple' to an Apple panel that has higher numbers, then there is decent chance it would be the SD; not XDR. The lower SD panel cost would help drive higher larger iMac sales ( because the iMac would have a lower price. Hence a larger target market).
If the larger iMac gets its own panel ( decoupled from both SD and XDR), then it doesn't necessarily need to take XDR size features either.
Apple may need a large screen iMac to prop up next gen XDR panel numbers. (e.g., XDR loosing traction in target market. ). So it could happen. It may likely happen (if that is the context), but not a 100% sure thing.
P.S.
Apple plans to update its 24-inch iMac to an M4 processor later this year,
I wouldn't bet on that one either. Apple let the iMac drift for well over a year. M1-> M3. They could do the same thing this year and into next M3 -> M5. It isn't a strategic product. MBA's can wait for a M4 until 2025 ... so easily could the iMac.