In that regards, we have some concerns about what might happen if people could hoard vanilla materials now for later conversion into RoS materials—If people could do such a conversion from old to new materials, then we think there would be a very real risk that people would near instantly craft their way to potential BiS gear shortly after the expansion is out, and thus if you could craft your way to the top right from the get go, then that would bypass or severely diminish the sense of progression and reward you would otherwise get from hunting for gear upgrades and crafting mats.
When Reaper of Soul goes live, the current plan is to convert your existing original crafting materials into what is currently the Inferno crafting tier, which will let people continue to craft all the items that they have access to now. Then once people start seeing new item tiers past level 61, those items will then be salvageable into new crafting materials that can be used to craft level 61 to 70 items.
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