In terms of AT&T plans for the iPhone 3G, the only thing that has been officially announced was the $30/month data plan. Anything else has a certain possibility (txt messages included with the package) until AT&T says otherwise. Everything that has been discussed on this board has been based on educated guesses.
Instead of anticipating AT&T making a surprise announcement that the iPhone 3g will indeed come with some number of txt messaging, I'm planning on just paying 30 bucks extra a month for the unlimited txt messaging family plan.