The 4K hasn't hit the meat of the market yet. The cheapest FF 4K recording available as of now is A7s+Shogun at about $5,000 (with media). When a 5D based 4K model comes out, it'll be somewhere around $3,500 (and no one knows specs yet anyway). For the three top hybrid manufacturers in Sony, Canon and Nikon, the bulk of the profits will come from products in the ~ $800-$2,500 range. Until then, they're letting their pro divisions serve as their testing ground and will wait out until the codecs (HEVC, I assume), the processing power and the media prices have come down sufficiently. In other words, some 60,000 units that GH4 ships is a drop in the bucket for the big boys. They're waiting until all the circumstances - including the 4K streaming and Blu-Ray discs - are working in their favor. Then they'll come out swinging with their big stick.
PS. Mind you, the above is about a consumer/enthusiast portion of the market. The high end/pro division has a slew of products out there already but those, obviously, carry a substantial "early adopter" price premium. That premium is getting smaller and smaller, however, and may be close to negligible within a couple of years.
My own prediction - and my batting average is around 50/50 here - is that in-camera APS-C/FF 4K hybrids will be seen within a year. Sony's A9/A99 (~ $3,500) has been bandied about for a while now. If that is announced at the NAB'15, then the floodgates will open in 9-12 months time to allow Sony to capitalize on its technological lead.
