The first line of the second Great Prophecy, which begins in the Heroes of Olympus series, claims "Seven half-bloods shall answer the call". Who do you think the seven half-bloods will be?
It will be necessary for a balance between the camps so they don't kill each other. In my opinion Percy, Leo, and Piper will represent the Greek Camp Half-Blood, and Jason and two of his friends will represent the Roman Camp. But who could the seventh half-blood be? My guess would be Annabeth, but it kind of throws off the balance.