Oh, I think the modding scene is as big as it's ever been.
And I'm not talking about "realy big mod projects", like the total overhauls and such. I just mean the multitude of smaller, basic mods. Like Ease of Use stuff, visuals (any triple A game like this will have HUGE visual modding interest), and considering it's a new D&D version, a ton of little rules mods, as many people will likely be longing for "how things used to be", at least in terms of minor details of the engine.