I read today a Dev Watercooler article in Blizzard's site, regarding the plans they had back then for Mists of Pandaria:
In Mists of Pandaria, Valor will be used to power a new feature that allows you to increase the item level of your existing epic items. This means that each week, you can become a little more powerful, hopefully allowing you to kill that boss that has eluded you thus far. There will be a bit of a game in trying to decide when to upgrade your gear versus hoping for a new piece to drop from a raid boss, but our plan is that even heroic gear can be upgraded slightly in this way.
(3rd paragraph, section "The Future of Valor")
Now that Mists of Pandaria is live, I haven't seen any NPC or anything like that that serves that purpose. Was this implemented? Scraped? To be released content?