It's completely unsubstantiated rumor asserted as fact
Look at the front page of this site for an example of what is simply wrong and misleading:
https://www.macrumors.com/roundup/iphone-6/
The blurb on the front page reads:
"The next iPhone is likely to come in larger sizes"
Note the use of the word sizes, the plural. Except there actually is ZERO evidence that the next iPhone will come in a 5.5 inch size. The use of the word sizes is simply bias.
All the rumors that say that Apple will try something different, from launching the iPhone 6 months early, are simply regurgitations of rumors that appear every year with the serial numbers filed off.
IF and I think that's a big IF Apple produces a 5.5 inch phone for early 2015 availability at the earliest, I see no way the phone isn't at least announced at the same event as the 4.7 inch iPhone. But if no such phone is announced, I sadly expect sites such as this to keep spreading rumors that just a few months later a 5.5 inch iPhone will magically appear and encourage waiting for nothing.
To repeat, if one simply follows one link at this site, the supposed 5.5 inch mockups are based on a claim they were for a 5.7 inch iPhone 6c. Does this make the slightest sense to anyone else?