Problem is, what are you gonna play it on? The best TVs out there are limited to 1080p, so it doesn't matter how many extra pixels the video has. It will downsize to 1080p so the TV will be able to display it.
High-end CRT displays can go beyond 1080p. For example, a Barco Cine 9 has a maximum resolution of 3200x2560. Digital displays are not the be-all and end-all that they are made out to be. As far as I'm concerned, they are 1 step forward and 2 steps back.