This has been hinted at for a while, and really isn't new. Matt has always said that low-quality links will hurt your SEO - the penguin update and disavowed links, sponsored content and nofollow, etc.
Google is just treating low-quality guest posts as advertorials now, which require nofollow links.
If you practiced writing low-quality guest posts, then yes, you might have to change your strategy. But knowing you, that isn't the case, so I would assume you don't really have to change much on your end :)