Well, we have been working on our new application for several months now. We still have a way to go before it's ready for release, so we recently decided to take the plunge and make this application work on Tiger only, taking advantage of some Tiger-only technologies such as Core Image and Core Data.
Of course, we don't know when Tiger will be available, but by the time we are ready to release our application, Tiger will probably be available. Hopefully it will have been out for a few weeks to give a significant of the Macosphere to migrate. (Experience tells me that users tend to move over pretty quickly to a new release.)