Some will, some won't. The market for a console @ $399 is by definition bigger than one @ $499.
Not necessarily, no. $399 might just mean Sony is taking a bigger loss to reach a bigger slice of the market faster. It makes more sense to lose more money to achieve a mainstream pricing, and I doubt they'd loss lead as far into $499. That is to say, I can see Sony doing a $500 console for $400; but maybe only a $530 console for $500. Will that $30 give you so much more that justifies crippling your reach? Probably not.
$600 console for $499.99 is the best case scenario for me. I know $399 has a bigger market, but $299 has a even bigger market so why not go there? I want something that isn't gimped day one like the PS4 was.