That's a very interesting question Soulfire, My guess is that they will not be spending so much time with the AI. Why?
1. The addition of dozens of spells makes it very hard for any AI to choose what to cast, on what target and at what location and time. This Increases complexity, unless the spells are dumbed down: no unit spells, no city spells, no global spells, no map spells (i.e enchant land, firestorm, volcano from mom), no item enchanting, no spell countering..
2. The developer will also include multiplayer. I'm not saying that stardock doesn't have the time to implement both a good AI and multiplayer together, but that makes a project much bigger than any galciv title released to date.
3. Multiplayer games have a stronger emphasis on the comunity of people that play together.And that also makes great business sense.
I expect the publisher to shift their focus to the balancing of the mechanics/unit balancing (treat the word unit here very loosely), and the general multiplayer experience, rather that fixing or designing a very good AI. I expect the AI code and its design to be "copy pasted" and adapted from galciv2...
Also, I really hope that I am wrong on this, but I doubt it 