KGI Securities analyst Ming-Chi Kuo, who has provided accurate Apple product information in the past (timing aside), has released a new research note predicting that supply constraints on key components may result in a serious delay in the release of the larger iPhone 6 model with a 5.5-inch display. According to the note, issues with the in-cell touch panel and coloring of the device could push the launch of the device back to a post-October date, possibly as late as next year:

We think the 5.5-inch model will also have issues with the yield rate of in-cell touch panel and color unevenness of metal casing. Indeed, these problems will likely be even more complicated with a larger size. In addition, from a technical perspective, we don’t expect sapphire cover, used for the first time on the 5.5-inch model, will easily pass the drop test near term. We are conservative about 5.5-inch iPhone launching by end-2014. Even if the product is launched in 2014, it is likely to take place after mid-4Q14, which is later than the September-October of consensus, with shipments being lower than consensus of 15- 20mn units.

The report goes on to note that the phone’s sapphire display (which we’ve seen recently in a scratch test video) may not prove sturdy enough in drop tests to go to market yet. Kuo recently noted that the upcoming iWatch, which will also use a sapphire crystal display, will enter mass production in November. Kuo predicts that when the larger iPhone 6 finally ships, fewer than 15-20 million units will be available.

While the same issues will reportedly affect the 4.7-inch model of the iPhone 6, the issues are expected to be more easily resolved for the smaller size. We’ve previously seen several physical mockups, part leaks, and display components for the 4.7-inch model, but not as many leaked parts for the larger phone. The new devices are also expected to pack in more dense LCDs, a more efficient A8 system-on-a-chip, new sensors, and improved camera systems. Apple will likely discuss the iPhone in September, while the Cupertino company is also planning smart watch and iPad announcements for later in the fall.