Rumors are a fun waste of time.
Now, they are not always innocent though. Considering the significant migration of high end users to Nikon these past few years, Canon has a huge vested interest in making us believe that they are still in the race.
Their all marketing strategy has been based for years on the notion that a majority of pros use their equipment because it is the best. We all agree that Canon still releases excellent lenses and good cameras, but the gap between the marketing theory of being the best and the reality of the cameras they have released vs the competition since the D3 in 2007 is putting this communication strategy at risk. Now it is DR/resolution, it had been high ISO image quality for years before that.
So every single high end shooter deciding to stay on board with Canon another week because of the belief that something is coming soon probably results in tens of indirect sales to the general public further down the road.
LL is mostly irrelevant because it touches such a small fraction of the photographic crowds that is mostly high end anyway. But Josh is right that DPreview is infested with rumors spreaders. There is no reason to belief that some of those rumors are not driven/orchestrated by companies themselves.
In my mind, the peak of rumoring happened a few months ago when false rumors were spread that the DxOmark DR results of the Canon 1Dx were going to equal those of the Nikon D4. The actual results were very far from confirming these rumors, so there is no doubt whatsoever that someone simply invented
this story. As Agatha Christie used to ask... "who does beneft from the crime?".
This is really interesting, because instead of focusing on product releases, that rumor (attack?) focused on one of the perceived root causes of the demise of Canon as a company seen as a leading sensor provider. DxOMark is of course simply exposing facts, but this is not relevant in a communication war. Facts only have impacts if they are known, so it is just as efficient to communicate falsely about the entity communicating the fact (DxOMark) as it is to communicate falsely about the facts themselves (like implying that something better is coming - which is understood by many as "we already have better technology today").
Why is it so important to win this war now? Well, because more and more photographers really are doing their last camera purchase for years to come. And the company winning the camera war hopes to also secure recurring lens revenue for years to come, with the multiplicative effect described above between pros and the mass public.