no gamebryo means modding is likely gone with it

Mod support as good as (or better than) Gamebryo’s is always possible, assuming the developers are willing and competent.

Bethesda surely understand how much they have benefited from modding over the years. Skyrim’s Anniversary Edition content is built mostly of mods, after all. So it’s reasonable to think they would at least consider making it a priority in a new engine.