There are plenty of people, like my brother in law (bought a 600D) and his brother (bought a 60D), who buy a DSLR with a superzoom in order to take stills & video of their kids with better quality & control than bridge camera, but with no wish (at least in present) to switch lenses for top image quality.
Agreed. I'm sure Canon sells a lot of EF-S 18-200mm lenses for just that reason, and that's the driver behind these patents. Canon certainly seems to like superlatives - the most megapixels, the fastest lenses - so making a bigger zoom seems entirely reasonable. Tamron has one, which they recently updated with their version of USM (called PZD), something Canon's 18-200mm lacks.
Considering Canon is making 10x zooms for professionals (the 28-300mm & 35-350mm) for a very long time, I (naively ?) think 15x zooms for amatures (maybe EF-S only) is not such a long stretch.
Personally, I've considered the EF 28-300mm f/3.5-5.6L IS lens on several occasions, for convenience and not having to change lenses. I have the 100-400mm, so I'm comfortable with a push-pull zoom, and unlike the 100-400, the 28-300 is weather-sealed. But every time I've come close to pulling the trigger, the optical compromises stop me. Still, the convenience remains tempting (although a 2-lens solution of 24-105mm + 70-300mm L seems more likely for me).