Intuition. And divine knowledge. (look up my nickname on Wikipedia

)
And now, seriously: In the past, when Amazon had been developing new models similar to existing ones, "traces" of it already showed up in the firmwares for the prior models. So, weeks before the PW was released, we already knew that it would have a light, and that its resolution would be 1024x758 (NOT 1024x7
68!). (I can't find anything better than
this right now, but rest assured that it was known... well before they officially presented the PW and raised the curtain).
So unless they have developed something entirely new, based on entirely different hardware and with a completely new software*... there won't be a new Kindle anytime soon.
As simple as that.
(*) I'm not ruling out the possibility. I just find it veeeeeeeeeeerrrrrrryyyyy improbable. But if they really did, then well - I was wrong, and I can live with it. But in that case, I'd bet that there would have been a huge announcement for an upcoming press conference.