One thing I think is definitely going to disappear in the next five years is third-party application repositories (aka "app stores"). Whether that be in the form of sketchy download websites, torrent services, or even the venerable Steam.
(In the coming analysis I'm discounting advanced persistent threats like the NSA or similar intelligence agencies as their motives and capabilities are completely different from that of the kind of malware we're concerned about here. APTs are mainly concerned about breaching a very specific target and ideally leaving no evidence.)