a new version, improved model, etc.:
an occurrence in which one thing is replaced by something better, newer, more valuable, etc.
So even if Windows 10 was nothing more than "hello world", it is still, by definition, an upgrade.
and before you get all "hurr it's M$ it's never improved/better AMIRITE?" That doesn't matter, the definition means it can be one or more of those separated by commas