Apple has updated it guidelines (PDF) for case manufacturers to include specific requirements and schematics for the iPhone 5s and 5c. As expected, the 5s schematics are similar to the iPhone 5 since the outer shell is largely unchanged.
The 5c design is more distinct from the 5, because while the internal layout is nearly identical, the exterior plastic casing is very different. See below for the 5c’s schematics.
In addition, Apple has added specific guidelines regarding the 5s’ Touch ID sensor.
1.3.3 Touch ID Sensor
Cases that are designed for the iPhone 5s must not inhibit the use of the Touch ID sensor. See Figure 2-1 (page 13) for the keep-out area.
Essentially, case designers must ensure that they do not obstruct the fingerprint sensor with their cases. We have already seen that Otterbox has had to redesign its iPhone 5 cases to account for this, by adding a hole for the fingerprint sensor.