Makes no sense whatsoever for an iPad 3 to appear later this year. Thought this prior to the keynote, even more so now.
Besides, what would they put in it? Higher res displays aren't magically going to become significantly cheaper in 6 months. More ram? For the mainstream target audience, hardly worth breaking the cycle.
The current cycle is pretty well timed imo - the iPad is more gift like than, say, an mbp, so they sell a tonne at Xmas when they've got a stockpile of 'em, then release a new one the following spring.
I'm pretty impressed by the update, very surprised they went dual core, it'd be soooo Apple to hold that back. Still question marks over the ram though.