The headline i read says they beat their previous record of 600,000 preorders on first day, obviously they not only beat it they destroyed it.
Preorders will only grow bigger in the future, since there are now 129 million iPhones out. Each new generation will a larger population upgrading.
Yes, only if they continue to choose apple products for their upgrade. The camera on this one sounds really nice, and the dual core processor is the best upgrade they've made so far in the cpu area imho.