Yes, as others have said this has been the racing favourite among book fans for some years now. It's not universally accepted and there are plenty of other theories out there, but personally I find the circumstantial evidence to be pretty compelling. (Also, GRRM has planned out those sorts of aspects from the book since way back, so I don't see him changing it in response to expectations - if we're wrong, we've always been wrong.)
To my mind, though, it's because of stuff like this that make the TV series - good fun though it is - so much less interesting than the books. The TV show is a single narrative telling a story, the books are a whole array of competing narratives and information and misinformation, and so much is deliberately planted to give you clues to work out the genuine state of affairs (insofar as there is one). The most important bit of back-up for this particular theory, for example, comes from a passage of Ned Stark's inner monologue in the first book - not a hint of which was contained within the TV equivalent. So if it does turn out to be true it's going to be deus ex machina as far as the TV viewer is concerned. (And even if it doesn't, there's plenty other examples which could be used to make the same point.)