I will start out by saying that these comments are speculative, based on what very little we have seen in card teasers.
We have seen a couple of cards that suggest a synergy between the spheres of Spirit and Leadership. Celebrian's Stone and Aragorn work together to encourage a Leadership/Spirit deck. The newly revealed Summing the Rohirim also encourages the same combination (assuming that Rohan allies are, like Rohan heroes, split between leadership and Spirit. And I think that's a safe bet).
My question is this. How do you think dual sphere synergies will work? Will we see a pair of of two allied Spheres (Leadership/Spirit and Tactics/Lore)? Do you think we will have a wheel of alliances (Spirit aligned with leadership and Lore, Leadership aligned with Spirit and Tactics, Tactics aligned with Lore and Leadership, etc.)? Do you think all six possible alliances will be supported? Do you think these cards are anamolous, and we won't see much dual sphere support out of the gate? Do you see us starting with one of these possibilities in the Core set and moving to another as the game expands?