The invitations showed what looks like an iPad. It's pretty obvious.
Whilst you can't be 100% sure about rumours, the good rumour sites will show rumours that have a reasonable chance of being true. As the release of a product draws close (e.g. MBP) then actual information about products becomes known.
As for Light Peak arriving in the Mac Pro we'll have to wait and see when it happens.
I dont have a problem with rumors closer to the announcement or more realistic ones. The problem I have is bigger sites like Engadget even publishing rumors about iPad 3 because some dick said it will happen.