It is still possible to upgrade from W7, W8 to W10. As to W10, Microsoft has written at length that W10 may be the last Windows. There are many articles about that such as https://www.theverge.com/2015/5/7/8568473/windows-10-last-version-of-windows
In the new W10 versions, features come and go and it's a rolling upgrade but the OS name is still "Windows 10."
Microsoft keeps updating Windows 10 every 6 or so months, does this mean, there will be no more OS upgrade?

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