What determines the quality of loot in horadric caches?

Ofcourse your character's level and the random factor affect what you get in the caches, but is there anything else that has influence on the loot from a cache? For example, does it matter on what difficulty I complete the bounties? Does it matter on which difficulty I open them? Anything else?

For clarification, I'm talking about the reward you get from completing all bounties in one act in adventure mode. A new feature in the Reaper of Souls expansion. Upon completing all bounties in one act you get a one time use cache which drops some loot when used. It usually drops a few crafting materials, some rift keystone fragments and a couple of blues and yellow. I've had one legendary so far out of 4 or 5 caches.

I understand there isn't nearly enough data from the community yet to answer this question based on results. But if someone had a link to a blue post explaining this or perhaps an ingame reference that answers this, that would be awesome.
Damn it, I might just spend the next few evenings farming normal - T1 caches and see if I get significant differences in drops :D.

As of patch 2.0.5. Caches have a greater chance to drop legendary items on Torment2+ difficult level.

Now have an increased chance to drop Legendary items on Torment II - VI

The cache will contain items that match the level of the game that the cache was received in. Even if you change to a higher level and open the cache. The level of the items will still be the level you received the cache.

The difficulty and level of the game when you got the cache determines the quality of items inside it. Where you open it makes no difference.

I was speed-leveling another character last night by having them create a T6 Adventure game, and got quite a few cubes during the process. I saved some to test if opening them in a T6 level 70 game made any difference, and it did not.

The level and quality of items in the cube always matched the level and quality at the time I got the cube. For example, a cube obtained in a level 20 T6 game always dropped level 20 items, along with low level gems and crafting materials. It didn't matter if I opened it in a different level 70 T6 game, or later on in the same game once the low level char hit 50.

The level/quality of items is determined at the time you claim the cache, not at the time you become eligible for it. For example, if you become eligible for a cache at level 20, but don't claim it until level 60, you will have level 60 items inside.