T-Mobile may not have rights to the term "rollover," no, that right belongs to AT&T, the nation's second largest wireless carrier. That didn't stop T-Mobile from pioneering yet another idea in the wireless industry though only to have AT&T follow suit with their own offering to compete. T-Mobile's Data Stash was announced at the companies most recent Uncarrier event which allows users to carry over their unused data to the following month, and today on January 7th, 2015, AT&T has announced that they'll be offering "Rollover data" to any of their customers that reside on any of their mobile share value plans, which is over 50 million subscribers.
AT&T is stating that all mobile share value customers will simply receive the Rollover data feature at no extra cost, beginning on January 25th. So by the end of this month you'll be able to start accruing any of the data that you don't use for the following full cycle and it will carry over to the next month. This is definitely going to be a great thing for some subscribers, but it will be a fine line where some users may end up saving so much data only causing them to realize they don't really need as much as they have.
In addition to adding this on to every share value plan at the end of this month for free and without a commitment, AT&T is also making it so that whatever data is rolled over from the previous month can be shared with anyone else on the same share value plan once it rolls over. Just like when AT&T introduced Rollover minutes, their Rollover data will work in much the same way where if a subscriber carries over any data into a new month, data used in that new month comes from that month's data allotment before dipping into the Rollover bucket. One other thing to keep in mind is that you likely won't be able to keep your Rollover data till the end of time. So for example, whatever Rollover data customers carry over once this begins, that first month's amount of data will likely fall off the following calendar year on the same date if it's still there. Basically, if it's like AT&T's Rollover minutes plans from before, you'll only be able to accrue rollover data for a year before it begins to recycle.