Apple has announced official launch date: Friday November 1st.
The date is also the first day of a new Hijri year (1st of Muharram 1435). STC, Mobily and Zain should all start selling the new iPhone on the same day.
Prices of the iPhone 5s are expected to be similar to the previous generation as expected with iPhones. LTE 4G support (Band 3 1800mhz) should be available obviously. FaceTime is disabled in iPhones dedicated to Saudi Arabia and UAE as usual.