Earlier this month, Verizon joined the ranks of T-Mobile by giving up selling two-year contracts, and now Sprint will do the same. Instead of locking customers into two-year contracts, Sprint will keep service and data plans on a month-to-month basis. This is meant to supplement their new iPhone Forever plan, in which customers lease their iPhones and pay a monthly fee of $22 in addition to paying for data. If customers stick to the iPhone Forever plan, they'll be able to upgrade to the latest iPhone when it becomes available. Last year, Sprint began offering a cellphone lease option, and according to the Wall Street Journal, Sprint says 51 percent of customers bought a new phone last year using this option. The iPhone Forever program is likely a reaction to the success of its leasing program.

Two-year contracts have appealed to customers because they offer the option to upgrade to a new phone at the beginning of a contract. But as companies phase out these contracts, the way people buy new phones may also change. With Sprint, Verizon, and T-Mobile getting rid of their contracts, AT&T is the only major U.S. carrier that will offer smartphone upgrades every two years. Whether or not AT&T will follow this trend is yet to be seen, but chances are it isn't far behind.