That looks accurate, actually. I think the only things it misses are the dead-ends where MS goes way too far to try to appeal to the end-user and rushes a poorly thought-out OS out the door. I'm talking about things like the infamous Millenium Edition. I've known people who used the steaming pile of crap known as Vista. I don't know anyone who ever used M.E. as their main OS.
Do you really think Microsoft would release Update 3 when the Technical Preview is around the corner? I clearly doubt that is going to happen looking at the conflicting Update 2 patches, some receiving the first patch without any hitches while handful of others facing BSOD. The Update 2 is yet to be finalized at the beginning of the weeks of releasing Windows 9 Technical Preview. There is no use for Windows 8.1 Update 3 in that regard. Just my little observation of things though.
Not sure this is a must . Installed all as offered by WU, means (the later revoked) update last patch tuesday (didn't uninstall), then 2993651 and yesterday 2993100 and 2979582, offered as 2975719 by WU with 460 KB. Machine is still running.
That Windows-9 is around the corner doesn't automatically mean that there is no need for a further support of Windows-8.1, especially as not every user will straight jump onto Windows-9. Just have a look around MDL and see how many are still refusing to move on from their older Windows-Version's. They just can't drop Windows-8 / 8.1 like that, especially with all the sold / still selling Hardware + OS - Bundles out there. Plenty Manufacturer's just don't care about Driver-Updates etc. for the next OS and not everyone is willing to buy every 12 month new hardware or simply not able to afford it.