confirmed that they will be introducing a more powerful PS4 with 4K output, but the company will not be showing it at E3. They still aren't getting specific about the features, or when it will launch, other than to say it will have 4K output and all PS4 games will work with it -- and it will be more expensive than the PS4.
The main reason for the PS4K is rumored to be in order to make the PlayStation VR work better, and to provide 4K output to support Sony's 4K TV business (the console may have a 4K Blu-ray player, which would be a strong incentive to buy for 4K TV owners). Note that this doesn't mean games would be playable in 4K resolution; that requires very expensive levels of graphics hardware unlikely to be found in a console that would (probably) retail for $499 or less. Although I could see making some cut scenes or an intro video in 4K for a game... a pure marketing feature.
Rumor still suggests that Sony will introduce this new console this fall, in conjunction with the already announced launch of PlayStation VR in October. Normally you'd expect a fall device to be introduced at E3, but Sony may be thinking that the PS4 Neo would drown out all of the other things Sony wants to talk about at E3. That's certainly a valid concern. By confirming the device before E3, Sony is no doubt hoping that they can focus on new PS4 titles at the show, and perhaps generate some pre-E3 buzz greater than Microsoft.
Also, Sony is doubtless trying to keep current PS4 sales from slowing down too much with a new console on the horizon. SCE head Andrew House confirmed that the current PS4 would continue to be sold; they will have both consoles on the market for the foreseeable future, separated by price and capabilities. But both will be able to run all software for PS4. (House said making software work with the PS4K would be relatively easy, though one would suppose that varies depending on how much developers want to improve the game's look for the PS4K version.)
There are risks here, though. Now that the PS4K is real, journalists and social media may still focus on that rather than new PS4 titles. You can bet there will be questions about every upcoming Sony title like this: "What will this look like on PS4K?" Also, knowing that a PS4K is coming, some buyers may hold off picking up a PS4, though probably most of those who really care enough about horsepower to pay more for a more powerful console already have a PS4. GameStop will probably get a bunch of PS4s as trade-ins when the new PS4K comes out.
Perhaps the greater risk for Sony is that it gives Microsoft a chance to capture more E3 buzz by actually talking about upcoming hardware. Microsoft is probably going to introduce a smaller, cheaper Xbox One -- that's a normal part of console evolution. Microsoft is also rumored to have a more powerful Xbox One in the works, codenamed 'Scorpio', that is rumored to be even more powerful than the PS4K.
Now, Microsoft may also want to avoid depressing Xbox One sales by announcing a more powerful console too far in advance. Rumors have suggested a 2017 introduction for the Xbox One Scorpio; touting it now would seems to hurt Xbox One sales, unless you offered some sort of upgrade plan. Which Microsoft could in fact do if they really wanted to; one of the big advantages Microsoft has over Sony is the immense amount of cash Microsoft has (over $100 billion at last count). Microsoft has been reluctant to use this weapon in the Xbox One fight up to now, but they could unleash it.
If Microsoft is really planning for a Scorpio launch in 2017, they'd be wise to keep its features unspoken for now. Let Sony and Nintendo reveal everything about their new consoles (PS4K and NX) by the end of this year, then Microsoft has a chance to tweak the Scorpio a bit to make it as competitive as possible. Yes, complicated changes would mean a delay, but simple things like choosing a higher clock speed for the GPU or CPU, or adding more RAM or higher-speed RAM could make a big difference in the specs without changing the timetable. That might increase the component costs for Microsoft, but they could certainly deal with a lower profit margin better than Sony or Nintendo could.
Of course, one of the big reasons to create a more powerful Xbox One is virtual reality (VR). Given that the Oculus Rift ships with an Xbox One controller, it's not difficult to imagine Microsoft would like to have an Xbox One Scorpio powerful enough that an Oculus Rift could plug into it. Or a HoloLens.
It will be interesting to see exactly what gets announced at E3 this year.