My dream team would be: alphinaud, thancred, lyse, Gaius, estinien, Krile, and tataru. But alas, we know it would never happen.

I think the safest way they can go, is to leave all the scions and introduce brand new set of characters. Especially if it's true that 7.0 onwards they want to have a more self contained story.

Mayhaps in the end of EW they will pull the "thank you for helping us WoL, now that primal threat is no more, let's disband the scions" and then everyone will go in their own separate ways and we do the same. We will continue exploring to new world/meracydia/etc. (though we can still visit the our scions friends), meet new people, basically become an adventurer again. If they want, they still can have some of the scions show up once in a while.