We do have plans for updating the trading system. Chris has made the following comment about what that is likely to include:
"
As for how it works, the current plan is a combination of public stash tabs (to make it easier to find items) and separately, an asynchronous cross-instance-website trading system. You can basically trade (without buyouts) across the game and website. The trades and offers are still there when you log in later, so it's possible to trade with offline people or people who aren't in your game area or are on their phone or work PC.
Unfortunately, we have no recent updates as to when this is likely to be implemented.
