Seems like Apple is taking a page from Microsoft's playbook as the company will be rolling out the macOS Sierra upgrade as an automatic update. Previously, Mac users had to locate the update on Apple's website but now it will be delivered automatically to everyone who has automatic update enabled.
This is the default setting so just like Windows 10 on Windows 7/8x PCs, the new Mac OS will be downloaded automatically on most Mac computers. After the download is completed, users will need to accept the installation.
Apple doesn't appear to be cramming its software as hard as Microsoft – you have to have automatic updates enabled and the storage space to take it, and you have to explicitly agree to the installation – but that's because it doesn't have to: Cupertino's customers are conditioned to be extremely loyal to the brand and take whatever Tim Cook and co hand out, whereas Microsoft has spent decades expertly fostering resentment.