At some point we want to do an expansion pack. And by some point, I mean, we have a pretty good idea of what, when, and what would be in said expansion pack. But there's a lof of "Stuff" involved in deciding what will be in an expansion pack and when it would be launched and how it would be packaged.
First a little primer: Unless you're mega publisher, if you want to be in the stores for Christmas, you have to be released by September 30th. That's the magic date. Secondly, unless you're a large publisher, having both a boxed version and an expansion pack on the shelves is really really hard.
So if we want to do an expansion pack soon, we would have to release it either by the end of September (any earlier would be too close to the original release) OR wait until next year (February 2007).
There are also two basic ways of going about an expansion pack:
The Traditional Way. You release your expansion pack for $19.95 to $29.95 that requires users to have the original game. This is what big publishers tend to do because they can have both the mega selling original and the expansion. Civilization IV and Civ IV: Warlords would be a great example of this.
The Alternative Way. You release an expansion pack that plays on its own for $39.95 to $49.95. That is, you basically update your original game to include the expansion pack as an integral part of it. Disciples II did this.
I don't have a strong preference. If you take the traditional path, you risk losing shelf space entirely unless you are selling in significant quantity. If you take the alternative path, you need to find some way to enable people who bought the original game to get the expansion pack without having to pay full price (rebate in box for existing players, or direct download or something). It also has the problem of requiring the existing game be taken off the shelves first to be replaced by the "new and improved" version which can be a real bummer.
Or you could just bypass retail entirely and offer it direct and not mess with any of the problem and release on your own schedule.