A few weeks ago, a card showed up randomly that claimed to be from Return to Ravnica. At the time, most of us passed it off as a really good fake because of the copyright line being incorrect. But then the newest IDW promo card showed up and used the same copyright language. So maybe Rootborn Defenses is actually real?
Also revealed at Gen Con Trade day is the Golgari mechanic:
Deadbridge Goliath 2GG
Creature – Insect (R)
Scavenge 4GG (4GG, Exile this card from your graveyard: Put X +1/+1 counters on target creature, where X is this card’s power. Scavenge only as a Sorcery.)
So this brings the spoiler up to 3 Return to Ravnica cards right now, but who knows how many more will show up during Gen Con?