Here are my very early thoughts:
Starting Pitching:
We certainly have something with Soroka and Fried. I don't see Keuchel and Teheran returning. Folty is not 100% certain to return, but I'm leaning to him coming back. One of the kids, possibly Anderson, will likely make the rotation and I think a vet will be signed. Early favorite of mine, depending on cost of course, is Bumgarner.
Bullpen:
We know Melancon will be back. Greene should be and I'd give Martin a one year deal to return. Newcombe has found his niche there. Obviously need another arm or two. Hopefully AA doesn't wait long to fix it.
Catchers:
Now we know McCann is retiring. With that now official, I look for Flowers to return on a one year deal. Unless Grandal's option is not picked up, FA market looks kind of weak. Braves may have to trade for one.
Infield:
1st, 2nd, and shortstop are set. The millions dollar question is whether Donaldson is brought back. If not, is Riley ready to take that place full time? Or FA, very unlikely a Rendon. Early gut feeling is Donaldson returns. Have to bring back Culberson and Camargo.
Outfield:
Only thing certain here is Acuña will be a part of it. The rest is up in the air. I do not think Markakis' option will be picked up. I think Pache and Waters are close enough to be ready, likely pushing Markakis out. Inciarte is not a sure thing to return as he could be in a trade. But at this time, I think he stays. I would like Duvall brought back.
So as I see it, if the below items happen, this could be the 2020 Braves:
Rotation:
Madison Bumgarner (personal preference)
Mike Soroka
Max Fried
Mike Foltynewicz
Ian Anderson
Bullpen:
Mark Melancon
Shane Greene
Chris Martin
Sean Newcombe
one of two FA
One of two minor leaguers
Possible Lineup
Ronald Acuña Jr (LF)
Ozzie Albies (2B)
Freddie Freeman (1B)
Josh Donaldson (3B)
Dansby Swanson (SS)
Ender Inciarte (RF)
Tyler Flowers (C)
Christian Pache (CF)