In early November, Microsoft announced a sweeping set of changes to OneDrive, specifically by dropping its free storage options from 15GB to 5GB, dropping unlimited free storage that came with some Office 365 plans, and by dropping some paid plan tiers. Of course, this caused a bit of a firestorm, and in December, Microsoft backed down, giving current OneDrive users the opportunity to keep their 15GB storage plans by opting in.
That offer has a time limit, however, and it's rapidly approaching. Tucked down into the bottom of the offer page, Microsoft details the time limit:
Offer must be redeemed by January 31, 2016. Microsoft account required.
The decision to cut back free and low cost storage was necessary, but as Microsoft CVP Chris Capossela later explained, the communications were "handled badly". As he explained it, "the way we did the communications was very rushed, because of a major publication that was going to publish something that was very damaging, and was not true. And so we felt like we had to get in front of it and we just weren’t ready."
In any event, if you haven't taken the time (just a couple of clicks, actually) to retain your free storage, be sure to get right on that, because after the end of the month you'll lose the opportunity.