iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
iPhone 3GS Launch Day Details and AT&T Pricing
The iPhone 3GS will be available for $199/16GB and $299/32GB for "new and qualifying" customers. The existing 8GB and 16GB 3G models can also be purchased for $99 or $149 (while supplies last).
On launch day (June 19th), two lines will form at 7 a.m. local time at the AT&T retail stores. Customers who had pre-ordered from retail stores will be able to pick up their iPhone 3GSs at that time, while customers who wish to purchase that day will have to wait until the store opens at normal business hours.