Going by that logic they can never have another baby since there is always another event, appointment, visit, etc. People can't really determine when they'll get pregnant. It could take a month, it could take a year.
I'm happy for them. I had a feeling she was pregnant at the visit on 5/8.
There isn't always something else lined up. After Malta no other overseas visits have been announced. This was also an added big deal as the Queen asked Kate to represent her for the first time.