It'll never happen. The problem is people would INSTANTLY be using it to sell champs for irl cash.

People bot-farming new accounts to get a decent lego or two and then selling the whole acct is already bad enough.

With 4 Gnut and 3 Acrizia, I could cash in LOL

Rat is correct in that will be something we're never going to see. I suppose there's a .01% chance or something absurd, but maybe not even that. 

If they ever do it would be a sure sign that the game is on it's very last days and about to be shut down.

Simple thing is this: Plarium won't allow trading because why would someone buy $1000 worth of shards to *try* to get whichever champ when they could instead pay someone $100 to trade them that champ, and plarium wouldn't see a dime of it.

Haven't we seen this chaos in EverQuest and Wow?