Not to mention all the modding that will be done.
There are so many different versions of "decisions" now-and this is by no means criticism, as they all simulate different things within the world even if the mechanic is basically a decision-that they seem a bit thin in a way that, say, traits and province improvements (two things I worried about) do not.
But what is most exciting about this game is that while Paradox seems to have done a much better job filling in the substance of the various mechanics than it did with initial EU III or Victoria II, it hardly matters. Good that they did-especially for new players-but it's just the beginning because they've gotten the platform almost exactly right. I have one or two problems with mechanics that can't be modded (at least not directly-like the absence of defensive claims, excessive truce length, universal MA), but by and large the mechanics are there.
Modders can now take the mechanics, and what is already an impressive amount of substance, and build upon them. Right now, there are what? Two dozen categories of plots, most of which are unavailable to the vast majority of characters? But the plot mechanic is there and the AI knows what to do with it. Same with decisions and ambitions. So give the community a little time and I imagine you'll see hundreds of new plots, ambitions, decisions, events, event chains, traits, etc.