It's really gonna depend on the state of healers for me. In Shadowbringers I went from SCH to DNC (for a bit) and swapped to AST because a) I got a healer itch to scratch, b) it's the only one of the 3 I can enjoy some content on and c) one of the WHM in my group wasn't enjoying herself with healing anybody because of how healing is ATM, so I swapped with her and let her play MCH (and sometimes swap with each other).

Sage has piqued my interest as a former SCH main (I was SCH main from ARR, HW and SB) that may be my choice.

But I might keep DNC as my DPS. Reaper might replace my melee DPS, depending on how will it plays but for Shadowbringers my set up have been:
Healing - AST
Tanking - GNB
Melee - SAM/MNK
Range Phys - DNC
Mage - RDM, but TBH I've rarely gone mage for anything

If thinks end up worse than they are now for healers, then I might end up giving up the role altogether and maining DNC, AST is currently holding me on a string.

I like variety, so I'll probably mix things up a bit throughout the patch cycles.

If they improve DRK then I might swap my GNB out for that. I used to tank DRK because I loved it and liked that was the more technical of the three and whilst it now flows well it feels like it has lost of a lot of the flavour I liked.