Think it'll be some kind of new weapon/gear reveal, or a new trailer for the story missions or gameplay. I highly doubt it'll be G-horn. I really don't think they would let Deej publicly advertise something like that when they've fought so hard to say that Xur is randomized and not set up every week. Even if it was the case, I'd think they would leave it as a surprise instead of hinting at it in such a subtle way