The only couple of reasons I can see Jobs keynote this event are (1) Beatles comes to iTunes (which seems unlikely to me due to the fact that they’re own event is the same day [time zone stuff hurts my head so I'm not going to pretend to know exactly how a Paul McCartney appearance would fit into Apple's, so I won't even try.])

and (2) Tablet.

Considering this is a music event, Tablet is a no-go for launch.

If the Beatles doesn’t go to iTunes, I see no reason for Jobs to shoot his appearance wad on mere iPod updates (camera or no) —

Jobs keynoting is big — it can only be the third coming of Steve Jobs once.

But IF he’s right and El Jobso comes to the stage, he’s going to be pimping more than iPods or even a new AppleTV. It’ll be the new tablet. He won’t keynote an event unless it’s the next revolutionary product.