The iPhone 5c and 5s launched on Sprint Sept 20, 2013 so they have passed their 12 month anniversary. It usually takes Sprint about a month after a phone passes its anniversary date before they actually start allowing their MVNOs to activate it. It looks like Sprint has fast-tracked approval of last years' iPhones on MVNOs. Sprint MVNO Ting, has posted on their blog that you will be able to bring a Sprint iPhone 5c or 5s to Ting starting Monday Sept. 29. Another Sprint MVNO Expo Mobile, notified its dealers that the iPhone 5c and 5s could be activated starting today, Sept 26, although it reportedly isn't working yet.
All the Sprint MVNOs are subject to the same list of blacklisted phones, so once the 2013 iPhones start working on one Sprint MVNO they should work on all of them that support using Sprint phones including Ting, Expo Mobile, Ecomobile, RingPlus, Kajeet, Real Mobile and Red Pocket CDMAS. Note that only iPhones sold for use on Sprint can be used on Sprint MVNOs, Boost and Virgin Mobile phones, including iPhones,will not work. Sprint iPhones can't be used on Boost or Virgin Mobile either.
Another phone that should be allowed on Sprint MVNOs soon, if not allready, is the 1st generation Motorola Moto X which launched on Sprint Sept 6, 2013. According to Ting this phone hasn't officially been released by Sprint for MVNO activation, but should be soon. However, a Ting customer left a comment on Ting's blog post saying that he and a friend were able to activate Moto X's on Ting a few days ago.
You can check ther release date of recent Sprint phones in my post Banned Phones - Tracking The Sprint MVNO Blacklist. Ting also has a page listing if and when hundreds of Sprint devices can be activated on Ting and other MVNOs.