I agree with you about the naming only in that the GX1 and G1X are confusing. Not about the evolution of Canon's G series however. And I totally don't understand your fear that P&S users won't get what the G1X brings to photography. Any potential buyer who reads reviews will have been told the lens tradeoffs that go with the bigger sensor. Those who just look at P&S cameras at the store counter would probably be put off by the higher price tag or at least question it. Any user who invests in a camera as complicated as the G series are will need to invest some time to learn it.
But you may be right, I'm one of those DSLR users. I use both full frame and crop and switch back and forth based on need. My G series cameras have met a need and there are few downsides to the G1X as compared to my G10. I've solved the close focus issue by using a 500D and soon a 250D closeup filter. The DOF issue is solved by stopping down. The size and weight differences between the G10 and G1X are insignificant at least compared to my 4 lb 5D + 24-105. Even with the closeup filter there is less than 1/2 lb difference between the two Gs. I won't notice that difference even when I'm backpacking.
You are right about the difference in close focusing in the underwater housing and that is a valid consideration. I will have to evaluate how important that aspect of UW photography is, I may just use my G10 for that. I'm serious about photography, but not serious about underwater photography or I'd have invested more heavily in it. The G1X's limitations there may well be acceptable.