P&S lens size versus sensor size

I have noticed that the many latest 1/2.3 BSI-CMOS sensor cameras often have zooms up to 450mm, yet with the latest 1/1.7 BSI-CMOS as in EX2F or just CMOS as in the case of the S100 or LX7, all these only have zooms up to approximately 100mm, and also often don't retract fully.

Is this an actual limitation, or is this an arbitrary limit maybe for the sake of higher image quality. I have been waiting for the new bunch of enthusiast cameras with 1/1.7 sensor and longer zoom, maybe in the range of 240mm. To me this might represent the natural limit of the larger sensor size.

Is this physically possible or am I waiting for a dream.

Brian