Thanks for taking the time to write this. It's definitely given me some things to consider.
I recently decided to stop playing the game myself and I actually decided it would be best for me to just sell the cards and invest the money outside of the game, for the most part.
I still have about $3000 worth of them left (they're not attached to this account) though, and was starting to think about possibly hanging onto them for a while. I have a lot of the Beta summoners left, for example. I could probably rent those out for a while. We'll see, though.
I'm keeping the Untamed cards for now, too, because I think it still remains to be seen what will be the fate of some of those.
Thanks for the comment .... glad to help. Liquidity can be an issue with cards.... but at this level of adoptions I would say its ok