This works to prevent players from purchasing on-level epics as soon as or even before they ding 80. At most a player can purchase one or two pieces before using up his or her Honor. Emblems work in reverse. It's impossible to obtain emblems below the appropriate level, but there is no upper limit to the number of emblems you can store. Unlike badge gear from The Burning Crusade, where higher tier items for more badges were made available later in the expansion, Blizzard has created different tiers of gear for different emblems. This means it's unlikely that there will be new items available for Emblems of Heroism or Valor.
This means you won't progress gearwise just doing the same thing over and over. In order to get better gear, players will need to raid. In contrast, because Honor is the single currency a singular currency across all levels for PvP gear, Blizzard is constrained as to how to limit accessibility to better gear. They do this by putting a ratings requirement on the best PvP items, requiring successful participation in Arena play. Arenas are to PvP are what raids are to PvE. It's not a perfect system, but it will do for now. But what happens when players reach the Honor cap and have every item they need or want?