I don't think that Maple would be confused with
Mabel too often. Most people are familiar with maple syrup, so they would probably think of that before they would
Mabel.
As for
Kate, I think that it could get more popular because of
Prince William's wife, but it has already been popular for a while, especially as a nickname for
Katherine,
Katelyn, and other related names.
A lot of people might assume that
Kate is short for something, but I've seen
Kate and
Katie used as full names enough times that I don't think it would be that much of an issue.
Most of the Kates I've met have been Katherines. I don't know the exact number, but I've known quite a few Katherines who have gone by either
Kate or
Katie. I used to know a
Kate whose full name was
Katie. She preferred
Kate.