Huh, no, not at all. The last 10 years have been spent increasing photosite density. Today's sensors can have 10-20 times the resolution, and be the same physical size or smaller.
Today's sensors are also more reliable, less sensitive to dust and noise than sensors made 10 years ago.
Sure it is, when we're talking about the same sensor and pixel design, which is implied when you say "simply swap the sensor". Otherwise it's a completely different camera setup.
Also, while obviously technology has improved, the industry doesn't necessarily move towards smaller pixels as a rule. To illustrate that: I work for a company that designs and produces image sensors, and I can tell you that we have one sensor product that has a resolution of just over one megapixel, but it's larger in area than our seventy megapixel product.
It all depends on the specifics of the project, and I can imagine that operating in space has certain constraints that prohibit just swapping in another sensor. These camera's are scientific instruments, and that means different rules apply.
