Red are advertising their camera by the number of pixels on the sensor, which actualy has 4.9k, of which only 4.5k maximum may be used for recording (when going uncompressed) when and if that options becomes available. Presently those that have red can only record using a 4096 by 2048 portion of the sensor. Sensor size is what all DSLR manufacturers use to advertise their cameras. As to the measured resolution, Graeme has stated it is more something along the line of 3K, here :
http://www.reduser.net/forum/showpost.php?...mp;postcount=19
So Red are advertising, just like most companies, to make things sound great. They don't specifiy if they're refering to sensor resolution or output (measured) resolution of the full color image. However, if you ask precise questions, they usually respond, and I don't get the impression they're doing false advertisement. They're just being smart and a little sensational, but who can blame them for that.
Cheers,
Damien