For consumers, the main benefits are being able to use a local carrier when traveling abroad instead of paying international roaming charges. It also means avoiding early termination fees as you would with an annual, traditional contract. Other than that, the pricing plans with carriers remain the same.
Apple will sell the unlocked phones for prices ranging from $649 to $949, depending on screen size and storage space. Locked iPhone 6s start at $199.
Read MoreApple to sell unlocked iPhone 6 in the US
It's not the first such move by Apple. A few months after launching the iPhone 5, it released unlocked versions.
"It could be that Apple still sells iPhones in partnership with operators and wants to keep that relationship healthy," Chand said.
The long-term concern for carriers like Verizon, AT&T and T-Mobile would be if Apple installed soft SIM-cards, which are not linked to specific carriers. Such an arrangement would mean a consumer would be able to switch to a carrier with a better plan, and that could set off a pricing war over service plans, Chand said.