Yeah, that I don't get very excited about.. Only noticed that option by the end of the post, but I decided to keep all the thinking through it.
Suggestion: What about a trading system between in-game friends only? There could be a Wishlist where each player would inform what's interesting for them and maybe the limitation of the trade happening only if the offered card is in the other's Wishlist, that way lots of garbage being offered in exchange of good cards would be avoided. Or maybe, if that's too much trouble to add to the game, at least we could have Wishlists here in the forum.
Even after the pvp addition, it still feels like there is too little interaction between players. I always felt in-game friends should have more privileges, maybe the trading system or a gifting option would add more fun to the game!
(I've seen interest on a card trading system in lots of posts over the forum, but there was nothing related to this in this thread for the past months at least, so I thought in making the suggestion myself. If this was already said hundreds of times, discussing on ways to how make the update possible would be very productive if the reasons why it hasn't been done yet were cleared out. c: )
Edit: The trading system would also estimulate people to invest more in their collections! And if the gifting option sound problematic, maybe there could be a limitation for x number of gifts sent per week/month - or even an special item for that, like the gift box that is used in Neopets for cash items.