I assume we're building up to a Darth Revan ...

I think there's a good chance we'll see Darth Malak, possibly as a legendary (ie needing 'any 5') but probably more likely to be a marquee.

I think there will probably be other marquee toons released between now and then who will be needed for darth revan, though I can't think who. Calo Nord would make no sense. I don't think we'll be able to do it with already existing toons because then where's the financial incentive?