First, default settings are never "consent".

Second, even if they did consent to automatic updates, that obviously applies to updating the current product they purchased. Upgrading to a different model is obviously not what people expect. Most people expect that their car will receive necessary updates (recall notices), which obviously doesn't include exchanging the car for next years model without some sort of additional contract.

Besides, it's obvious why Microsoft is forcing out the download - they are using download numbers in their their marketing strategy. (i.e. the astroturf headlines claiming "{N} Million User Download Windows 10 in {TimePeriod}")