Given Canon's past history of releases in February and August, and the roughly 3 year cycle for 'pro' bodies, I would expect any announcement this August, before Photokina. I doubt if their problems with the I series has any relevance. And they have got to upgrade sometime - that's the name of the game these days, upgrade constantly or wither and die. I don't think that the 5 series will disappear, though it might appear under a different label - 3 series, perhaps.
The faff about the book announcement in amazon.com tells me that the publisher expects an upgrade, and is putting down a marker; perhaps they have an NDA, but then perhaps it's only intelligent guess work.
Amazon regularly lists books due for publication months in advance - nothing new about this.