That has only happened once in six gens.And before gen 6 he always had the grass type start/a grass type, but that didn't stop him from skipping out on getting a Grass type in gen 6. Also he always had the regional bird in the past generations but now it looks like he will skipped it in this generation, the point being is just because he had a water type in the past generations doesn't guarantee or mean that he will get a water type this generation, although it is a possibility it's not guaranteed.
I know some people would say that oh well it would be weird for Ash to skipped out on getting a water type this generation given the setting, but in all reality just because people may find it weird for Ash to skipped out on a water type this generation doesn't mean that it won't happen. Plus the writers have been pretty unpredictable this generation so the fact that so many people are expecting Ash to get a water type could wind up actually meaning that the writers won't give him one because of most people expecting him to get one.
At this point it could go either way.