The most notable currency change in patch 6.0 will be the removal of Valor and Justice points from the game—you can see the reason for this change here.
If you’re currently working on the Mists of Pandaria legendary quest chain, don’t worry—the quest Test of Valor will be removed from the game in patch 6.0, but you’ll still be able to progress with the quest line and eventually earn your awesome cloak! Also as a result, item upgrades will no longer cost Valor points, and can be completed using Lesser Charms of Good Fortune instead. On the PTR, each upgrade level currently costs 50 charms, but it’s possible that this value will change.
You will also be able to turn in your Lesser Charms of Good Fortune for Warforged Seals. The restriction on the weekly turn-in quest for Warforged Seals is being removed, so you’ll be able to get as many as you can afford.
Finally, almost everything that is currently purchased with Valor or Justice—such as heirloom items—will be available to purchase with gold. As always with game content on the PTR, any prices you see may end up changing with the actual release of patch 6.0.