For the avid collector, inventory problems have reached critical mass in Mists of Pandaria. The previously announced toy box and heirloom storage will arrive with the launch of Warlords, but many are still wondering what to do with their ever increasing transmog collections. A solution is on the horizon, but it won't arrive until sometime after the expansion's launch. If the already announced inventory improvements aren't enough, there will also be slightly larger bags added in Warlords. These will probably be 30-slot bags, and I would be surprised if there is ever a larger bag than that once the inventory changes are fully implemented.
When it comes to what items will qualify as a "toy box" item to be removed from your regular inventory, Blizzard will be adding these on a case-by-case basis and looking for player feedback on the future beta and PTR to help identify items they may have missed. For example, should a trinket such as the Super Simian Sphere be turned into a permanent toy instead of a trinket? What about a popular quest item like Dartol's Rod of Transformation?