This theory definitely sounds logical, and I would love to see it happen if it'll involve Draco ;-) Also, JK just said in one of the new interview that 'Ravenclaw's days would come', maybe there is a Ravenclaw Horcrux that Harry would need help from a Ravenclaw to open too? That'll be quite an interesting way of uniting the houses, though rather focusing too much on individuals and not enough group collaboration?