If you have a reasonably good projector now, I'd say no. 2k is more than adequate unless you sit very close or are talking about 100"+ screens. Dbphd has hit the nail on the head. A 2k projector with JVC blacks, DLP sharpness, the ANSI contrast of a Kuro and 2000+ lumens of brightness would look far better than any current 4k projector.
I really don't think 4k will take off until we have really big and affordable OLED or projectors with a superior light source to lamps.
I really don't think 4k will take off until we have really big and affordable OLED or projectors with a superior light source to lamps.