Why not ask the people who say so?
A possible explanation: there are rumors that Apple will launch a new phone in the fall. Some people call that phone iPhone6, other people call it iPhone5s. And only when launching Apple will reveal the real name.
It's said that iPhone5s and iPhone 6 are to be lauched in September and iPads and iWatch in October.
Why iPhone5s and iPhone6 at the same time?
iWatch seems worthy a try.