They really shouldn't make Flash completely unavailable to download. They're cutting off a lot of legacy content with cultural significance. Yes, using unmaintained software is bad for security. However, the alternative of forcing people to use third party sources—which will all be somewhat shady, since Flash is technically under copyright—is even worse for security! Now, you might be downloading a fake, malicious co…
I do think it would be cool for them to keep offering downloads of the installer. Adobe should be proud of shockwave and show that pride by keeping the installer out there.