Larian has already confirmed there will be three modes: Balanced, Explorer, and Tactician. There is no reason to expect any of these modes to be closer to DND core rules than any of the others. There is no reason to expect that Larian will add more modes after launch.
Those are difficulty settings not game modes or rule sets. Big difference. The rules of the game are identical across all difficulty settings...with the differences being more enemies or enemies have special weapons or extra resources of some kind to make encounters more difficult on tactician or if you go the easy route you get +2 to proficiency on top of the usual proficiency bonus.
