Without giving the card abilities away, I expect to see more of these decks:
Forest decks that are faster
Air decks that are even faster
Card denial decks
More players experimenting with old factions they haven't played with for a while
Players experimenting with factions they have never played with
I have now unlocked all minions. Since I will probably be months unlocking the other cards, I wanted to offer my initial impressions before they are no longer initial impressions.
First, as I'm sure the goblins are already well aware, fire prism is badly broken -- at best the game will degenerate to a contest of who is lucky and draws certain cards first; at worst, it leads to invincible decks. At the very least, it should not impact barriers and not trigger more than once per turn -- but even this is probably not sufficient to balance it.
Other than fire prism, the cards I've seen (which include the seven minions and fire prism, betrayal, and brainstorm) seem like wonderful additions. Each has a very unique power and several either open up new deck possibilities or make old decks more playable. Only the unicorns, illusionists, and betrayal spell do not appear to me to have potential as a cornerstone for a deck, but all three have a very general usefulness in many decks. In fact the triton illusionist has a subtle power that is so interesting, I want to play ocean again -- despite the aquamancer that ruins that faction for me.
So thank you to the goblins for this wonderful addition to a game I love. And I'm awaiting a fix for the fire prism :)