On the cusp...

[thejeff]

Not so much that the majority of games are multiplayer, but that the majority of the developer's interest is.

This would require a very different model for turn processing and probably use up a lot of memory, since so many things would have to be done conditionally.

About the only thing that could be done ahead of time is planning the AI orders. Once mages start casting spells, pretty much anything may change based on the results of ritual attack spells, new globals etc. Everything preprocessed would have to be held in memory waiting it's turn to actually happen. I doubt you'd get much time savings in any moderately complicated game, which is where you'd want it.
Nor would it be a simple programming task.