Epic gems will come in patch 4.3. They'll not be prospectable from Pyrite or anything else -- instead they will drop from geodes on raid bosses. This may not be the final design, but it's what Blizzard has decided so far. The people who need the gems most are going to be the source for the uncut gems, and the quantity available will be very low.
Every time I've talked about this before, I've hedged my bets that Blizzard might drastically change the design for epic gems compared to the last expansion. As things turn out, it did, and we're going back to a design reminiscent of epic gems in The Burning Crusade, which were mostly available to raiders. Everyone who stockpiled Pyrite now has to decide what to do with it.