I disagree. An effort to make the core more attractive now @ $250 wouldn't attract that many new customers and might steer the ones that can be seduced @ $350 towards the lower margin Core rather than the Premium. At the moment, I believe MS is confident to grow their market share slowly building on Live and downloadable content with the Premium SKU providing a 'value for money'-proposition compared to the PS3.Rather than have a SKU available at $250, with a strong value, to propel christmas sales. They've opted to make the core an even worse value, making the only reasonable entry point $350, a full $100 higher than what it could potentially be.
All I can do is laugh at this point, MS is basically teaching "How to Blow a Golden Opportunity - 101"
IMO, they won't be giving the Core any legs until they think it will be able to target larger groups of consumers that are not currently attracted to the Premium. Probably at the 'magic' $199. If they want to push some numbers, I believe we might see (MS backed) 'specials' at that price come this Christmas, but that it won't officially drop that low until around this time next year.