They are likely going to have to trade someone we wouldn't expect, else the team will largely be the same again. I suspect Russell is gone, but he is not longer part of the core. Likely Happ sticks around as the Cubs have him under control for awhile and his value isn't particularly high. Almora could be gone, could stay, but at most he is in a reserve role.
So out of Rizzo, Baez, KB, Schwarber, and Contreras, I'm expect 1 or more to be moved in a more dramatic deal. If I had to guess, I think Schwarber will be traded after a decent year and one of KB/Contreras as the other surprise move.