They are not working on a 4k model yet. The hardware (screen resolution) is simply not currently available. Here is the exact quote from the article: “You can’t imagine what it’s going to look like when it’s 4K,” he said. “It’s not now, but it’s coming.”. He's basically saying given the natural progression of the mobile…
Actually if you just want that, hold tight a couple of months - there are a lot of small companies making alternatives to the rift. At the last Bossa Studios Occulus meetup I went to there where no less than 3 groups showing off their light alternatives. (although one group was pretty keen on going toe to toe with occulus…