Rights to Epix were included in the recent deal Directv signed with Viacom. The way I understand it, Directv has the rights to Epix at a set price for the next year if they choose to add the service, however it was Directv's call as to if/when to offer Epix.
From the press releases, it sounded as if Directv had no real interest in Epix, but had no objection to having the option in the contract. It was more of a face-saving effort on Viacom's part so say, "yeah, Epix was part of the Directv deal."
That probably doesn't answer your question, but then the only source that truly can is inside Directv.
Yeah, I have a feeling the only way DirecTV would consider adding it was as a separate tier in its own, and I'll bet the option contract is not set up that way, so they won't be adding it. But who knows.