On 28th August (during the maintenance next week) Patch 5.0.4 will hit live servers.
Currency (Valor/Conquest Points) will be converted the following way:
PvE: VP (Valor Points) will be converted into JP (Justice Points)
PvP: CP (Conquest Points) will be converted into HP (Honor Points)
Neither of the resultant currencies will have a hard cap (JP & HP) before the release of Mists of Pandaria.
Arenas will be closed, bosses will no longer award Valor Points, but rather Justice.
All items formerly purchasable for Conquest/Valor will be available for Honor/Justice.
After Mists of Pandaria Release on 25th September:
Valor can be earned again. The cap is 1,000 per week and the hard cap (maximum) is 3,000.
Valor will be used to purchase ilvl489 powerful PvE armor in Mists of Pandaria. (In addition reputation with MoP factions will be required).
Conquest will become earnable. The cap is 4,000. Arenas & Rated battlegrounds reward Conquest.
Conquest is used to purchase ilvl483 PvP gear, from Pandaren battle masters on the Great Wall.