In his latest Power On newsletter, Gurman mentioned that these iMacs are still in the early stages of development, so he doesn't anticipate them to be launched until late 2024 or possibly sometime in 2025.

Gurman previously stated that Apple is developing an iMac with a display larger than 30 inches, and now he suggests that this AIO PC will feature a 32-inch screen, similar in size to Apple's premium Pro Display XDR. Released in December 2019, the Pro Display XDR boasts a 6K resolution for Retina-quality content and starts at $4,999.
Apple has ceased production of the 27-inch iMac and Intel-powered iMac Pro for several years now and has yet to introduce a larger-screen iMac with silicon chips to replace them. Instead, the 'Apple House' offers a temporary alternative with the 27-inch model combined with other Macs featuring M-series Silicon chips.
Currently, the 24-inch iMac is the only AIO PC sold by Apple. The current model with the M1 chip was released in April 2021, and Gurman anticipates its successor to arrive in the early next year with the M3 chip, built on the advanced 3nm process. Let's stay tuned for more updates!