I'd tend to agree. It's almost unthinkable that Nikon could get a new model to final spec and prepare marketing material for it without it getting out via more plausible routes. I'm not clued up on the D300 specs but a brief scan of that brochure doesn't seem to show anything new. Besides, it doesn't fit with Nikon's recent incremental naming protocols - I would expect a D300s/x or D400 to follow the D300.