Paczkowski is well-respected and is a reliable source. If he's saying it with certainty then there's an extreme likelihood it is true.
It will be interesting to see how Cook performs since his style is very low-key compared to Jobs. There is no doubt Schiller, Forstall, Ive and Cue will be there to lend assistance.
It's extremely likely that there is a plan for an event on this date at this time. But since it hasn't been announced, it's also quite possible the date will slip, because they can let the date slip if they wish. So it can be both a reliably sourced fact and something that might not happen. Fun!
It will be interesting to see how Cook performs since his style is very low-key compared to Jobs. There is no doubt Schiller, Forstall, Ive and Cue will be there to lend assistance.