Along these lines, would an autopilot ever think of landing in the Hudson? (Particularly if it hadn't been done before?)
That's not correct. Ditching is very hard. Mess up your angle or sink rate or roll even slightly and you'll be in pieces. Same if the water doesn't cooperate.
One interesting thing is that it happened with an Airbus. The flight computers actually modified Sully's inputs on pitch by about 2 degrees, which ensured a softer splashdown than what Sully was commanding.
But that was a very subtle adjustment. Sully was an experienced pilot, with Glider training too.
It was not considered a serious option.