My guess is that a new Airport Express will be available after October 4th ... probably closer to whenever they put a date for iPhone4s/5 and/or iOS5.
My reasoning is that they've delayed the Express for so long, that the new ones will have features that are directly tied into features found only on iOS5 and the new iPods.
I have no information, nor have I read/heard about any rumors of such. It's just a WAG at this point.
I don't think you'll hear any information about a release date until the week before it does show up. No one's breaking down doors or bribing the manufacuturers for info like they do for the iOS devices.
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