You are 50% wrong in your assumptions

It is true that the higher megapixel capability of many DSLR cameras is not needed due to the 1920 x 1080 Res. BUT the larger sensor has a very important impact and it is the reason that many film makers are using DSLR cameras. It provides 1. Better low light capability. 2. Better control over depth of field. 3. Much greater dynamic range. You wont get the same benefits from 3 x 1.4" cmos sensors and you certainly won't get it with only one 1/4 " sensor.

Having said that you need to be an enthusiast to get the most out of the cameras capability. and 95% of the video shooters who are just shooting family, holiday photos and even weddings etc would be better served with a video camera