Sounds like they're flipping all the platforms to the north side (track 1). This has construction advantages (minimal impact on current low-level platforms while work is going on) and also design advantages (handicap access could be cut into the embankment vs having to use the overpasses for access).
That's pretty much it though, the space to work with is really tight where it is now alongside the Pike. It would be much easier I imagine to build new platforms on the other side. Now both platforms would be nice to accommodate Indigo but not necessary.