Why on earth does the download page for the Windows version 1.4.1717 state that Windows 10 is required? I have successfully downloaded and installed this version on Windows 7. But I almost didn't even try because I initially believed the claim.
On that note, dropping Windows 7 support would be absolutely catastrophic for me and (I assume) many others who've opted to stick with Windows 7. Thanks for continuing to support it, and please do not stop.
Windows 7 is no longer supported by Microsoft itself; it is almost 2 years past EOL. For this reason, it's no longer possible for us to test on Windows 7 or support it officially. It's very possible (and, as you've noted, even likely) that RStudio will continue to work on it, but we can't guarantee it.