Mac Pro models without a T2 chip, including the MacPro6,1, haven’t been updated.Mac mini models without a T2 chip haven’t been updated.MacBook Pros up to and including MacBookPro12 haven’t been updated, but from MacBookPro13 they have.MacBook Air models without a T2 chip haven’t been updated.MacBooks up to and including MacBook8,1 haven’t been updated, but from MacBook9,1 they have.iMacs up to and including iMac16 haven’t had a firmware update for several months, but from iMac17 onwards they have recently been updated in macOS 11.4.All Macs with a T2 chip, and M1 Macs, have had firmware updates in macOS 11.4.Similarly, those Macs whose firmware isn’t updated during the May-August period are those which are most likely to be unsupported by that major release. In a good year, the updates released in that period may remain current until well after that major release. Some time between May and August, Apple likes to release firmware updates which come close to those required for the first release of the autumn/fall macOS. It has made it clear in its version numbering that the next major version of macOS will be 12, rather than 11.x, and a little speculation following firmware updates suggests which Macs it will support. If Apple is true to its annual cycle of operating systems, it will announce macOS 12 at WWDC next week.

Mac os 10.12 review