Just to clarify, most people who buy the PS4K who already bought the PS4, are likely going to fund the new purchase by reselling or trading in their existing PS4, and the sale of that traded in second hand PS4 still means one less 'new' hardware sale for Sony. In other words, Sony could gain a new PS4K sale from an existing PS4 buyer, but potentially lose a sale from whoever buys their second hand PS4 unit. Though it still paves the way for accessory and software sales which Sony could profit from.
Also, whilst a mid-cycle release does allow them to be a bit more reactionary in terms of tech advancements, I'm not really sure hype and media attention is necessarily all one sided or positive. As the leaks of the PS4K show, it's drawn as much negativity as it has positivity, as many existing PS4 owners are pre-emptively feeling short changed, or others are annoyed at the prospect of having to spend more money on mid cycle iterative console releases.
Anecdotal I know, but throughout the day I've been talking to my casual gaming friends and relatives about this, and I'd say the majority (though not all) have had largely negative outlooks or responses to the news. A few who don't yet own PS4's however, seemed more optimistic about it, though their optimism seemed dependant on the price of the new system.