ARRI's new ALEXA SXT (Super Xtended Technology) cameras represent the next exciting step in the continuing evolution of the ALEXA family. Retaining the rock-solid foundation on which ALEXA is built, ALEXA SXT cameras additionally offer ProRes 4K recording, improved image quality, powerful color management and three fully independent HD-SDI outputs.


With in-camera recording of ProRes 4K UHD (3840 x 2160 pixels) and ProRes 4K Cine (4096 x 2637 pixels), ALEXA SXT cameras are the ideal choice for productions that need 4K UHD TV or 4K DCI cinema deliverables, so filmmakers can continue using the ARRI ALEXA platform they know and love.

http://www.arri.com/news/news/new-al...eras-for-2015/

So, that's the new "4K" ARRI camera.