People who have been told or heard about the whole mess would have already opted in to retain their 15+15 storage. The uservoice page, which Microsoft is using for their OneDrive feedback, that called for reverting the change garnered over 70k upvotes. MS's response on that page also included a link for people to "opt-in" to retain their 15+15GB cloud storage. Eventually everyone will know about it.
The article title is a bit misleading, however. Microsoft didn't really back down. They merely gave people a choice if they want to retain that storage they were using/given. Granted, this isn't the best course of action. But at the very least, it gives the OneDrive users, along with any Windows 8/10 users out there, the option of keeping it. I still would have preferred if Microsoft truly backs out of their proposed change. Because once the change takes effect, OneDrive is worse off than Google Drive and Box.com's base offering, yet slightly better than what Dropbox offers initially.