I'm really hoping to be able access my slingbox via atv.
I think (hope) one of two things happens- either an iOS update in the future will enable downloading of apps onto atv. One big issue here, at least as I understand it, is that the atv has limited on board storage- which is intended for buffering. Perhaps a v.2 version will have more memory.
The alternative is an updated version of the iphones/ipads slingplayer app that supports video over airplay. Given Slings track record with prior updates, if this is even possible (no system/OS constraints etc.), we could expect and update in 2015.