If Apple takes into account its macOS development schedule of the last three years, it will release Big Sur on September 27th. This minor MacOS Catalina update is the last unrelated security issue.
Apple last Wednesday updated MacOS Catalina, probably for the last time, except for security patches. This update — the sixth since Catalina debuted in October 2019 — is also a sure signal that MacOS High Sierra is nearing retirement. Catalina 10.15.6 brings a very short list improvements to Apple News, fixes two bugs, and adds an option to optimize video streaming on HDR-capable Mac laptops. Apple said the option will extend battery life for frantic streamers.
This update also fixes 19 security vulnerabilities in 16 of Catalina’s components, ranging from audio and core to messaging to WiFi. Most flaws, without a fix, could have let criminals run attack code on a compromised Mac. MacOS 10.15.6 will likely be the last non-security Catalina update. Over the past three cycles — Mojave, High Sierra, and Sierra — Apple has released six non-security updates for each edition; the previous four reached five updates each.
A regular schedule
Likewise, Security Update 2020-004, also released on Wednesday, was almost certainly the last for macOS 10.13 High Sierra, the operating system released by Apple in September 2017. Apple supports the latest edition of macOS ( call it “n”) and the two before that (“n-1” and “n-2). When a new edition launches – Big Sur coming this year – the oldest (n-2) falls off the support list. This n-2 is currently High Sierra.
More tellingly, Apple usually releases the last non-security update for the then-current edition about 10 weeks before its successor is released to the public. Last year, for example, Mohave’s latest non-security update, 10.14.6, appeared on July 22, 77 days before the release of Catalina. In 2018, the last non-security update for High Sierra, 10.13.6, appeared on July 9, 77 days before the launch of Mohave. And the year before, Sierra’s last non-security update, 10.12.6, was released on July 19, 69 days before High Sierra was launched in its final form.
Step 1 for ARM Macs
Three-year average gap between the last non-security update of an edition and the release of its successor: 74.3 days. The last three macOS upgrades were all released on a Monday; Catalina on October 7, 2019; Mojave on September 24, 2018; and High Sierra on September 25, 2017. If Apple sticks to this model, it will release Big Sur (ARM and x86 chip support) to the Mac App Store on Monday, September 27, 75 days after Catalina 10.15 was released. 6.