In July 2023 Business Korea posted a rumor report on an Apple foldable due in 2026 followed by a Ming-Chi Kuo rumor back in March 2024 that Apple's first foldable would go into mass-production in 2027.

Today, Apple analyst Ming-Chi Kuo is back with an altered prediction and new revelations as noted in his 5 key points as follows:

1. Panel supplier and possible size spec: LGD is the exclusive panel supplier. In addition to the 20.25" option, Apple is also considering using an 18.8" panel instead. The difference between these two sizes is their folded form factor, corresponding to the design of 14–15" and 13–14" laptops, respectively.
2. Production schedule and processor: The target mass production schedule for the panel and assembly is 4Q25 and 1H26, respectively (compared to the previous estimate of 2027). This product is expected to use the M5 series processor.
3. Crease-free panel as a design goal, resulting in very high panel and hinge costs: Apple aims to make the panel as crease-free as possible, requiring high design specifications for both the panel and the hinge. As a result, the cost of the panel and hinge is very high. Current preliminary estimates put the panel and hinge costs at around $600–650 and $200–250, respectively. If production yields improve significantly by the time of mass production, these costs could decrease.
4. LGD (panel) and Amphenol (hinge) are currently Apple’s exclusive development partners: A high level of integration between the panel and hinge is required to address the crease issue. LGD and Amphenol are the exclusive development partners for the panel and the hinge, respectively. Based on experience, Apple typically collaborates with only one manufacturer to focus resources on overcoming the manufacturing challenges posed by innovative designs. For example, the iPhone 15 Pro Max’s tetraprism (periscope) camera was developed in partnership with LGIT (module) and Largan (lens).
5. BOM cost/pricing and shipment estimates: Given the high cost of the display and hinge, the foldable MacBook is likely to be expensive. Unless Apple can significantly improve yields and reduce costs before mass production, the BOM cost of the foldable MacBook could approach that of the current Vision Pro. However, due to the more defined product positioning of the foldable MacBook, the shipments are expected to be significantly higher than those of the Vision Pro. Shipments are estimated to exceed 1 million units in 2026.

By the time it arrives it will have been at least decade in the making in an evolutionary way, as most of Apple's big devices have taken.  Of course when it arrives, Apple is likely to charge an arm and leg for it  -  unless competitors force them to be competitive. Then again, I know that's hopeful thinking.