They stopped making the iPhone mini so it felt quite a believable rumor. I think most of us assume at some point they'll do a major redesign that will break band compatibility leaving some of us with a big collection we wont know what to do with.
My personal hope at this point is they've kept the same connector and sizes for so long, that if a new redesigned Watch is released they may continue the old style with the upgraded internals as some kind of "Classic" model to keep the old band collectors happy. Just doesn't sound financially viable for Apple.