You can now buy the iPhone 6s and 6s Plus unlocked from Apple
Prices for an unlocked iPhone 6s start at $649 (16 GB model), while an unlocked iPhone 6s Plus can be purchased for as low as $749 (16 GB). If you're ordering an unlocked iPhone 6s or 6s Plus right now, regardless of color and internal memory, Apple says it can ship it in 2-3 weeks.
The unlocked iPhone 6s and iPhone 6s Plus are offered by Apple with no nano-SIM card inside, so you'll have to get one yourself. The unlocked handsets can be used on your carrier of choice - Verizon, AT&T, Sprint, T-Mobile, or others.
Apple already sold over 13 million new iPhones (in the opening week-end), and it will certainly continue to sell millions more around the world. Considering the fact that both the iPhone 6s and 6s Plus are quite expensive (especially if you don't want the 16 GB models), would you buy them unlocked, rather than on contract?
source: Apple via MacRumors