"Will those improvements finally make Android a match for Apple iOS, which has had an unbroken six-year streak of being malware-free?"
This is such misinformation. iOS had bunch of malwares, and only claims about "no malware" were for non-jailbroken devices. But then you should have compared that to non-sideloading Android ... and note that by default, sideloading is NOT enabled, just like by default iOS devices are not jailbroken.
AND even non-jailbroken iOS devices did have malware, like for example http/www.forbes.com/sites/timworstall/2012/07/07/there-is-too-malware-on-the-iphone/
So, you have two false claims, or bad reporting, issues:
1) you compare non-jailbroken iOS devices with Android devices where sideloading is enabled
2) even for non-jailbroken devices, your claim of "six-year streak" is false
I agree with gmuser on the falsification of the article's claims but for another simple fact. NO and I mean NO operating system is without malware/virus issues. Even Linux which Android is loosely based on (Android uses the Linux kernel and a very sophisticated Java machine) has issues with virus' and malware. Maybe to a lesser extent than Windows or Apple but it's a case in point. Benjamin Franklin once stated that "there is no secret between three men unless the other two were dead."
If Android becomes walled-off like iOS, it will lose its main diferential. There are many apps that are not in the App Store for n reasons (like TubeMate) that I still need to sideload. Still if one would prefer the security of walling-off, just don't set the option or mind the apps that you are side-loading.
So, the issue isn't the OS, but the user? Since the OS has that option disabled by default (just like, say, USB debugging), why the fear-mongering? Is really simple: you don't know what you're doing, leave everything at default (secure). You do know, tinker with it as you wish.