What I said in Photorumors about the same thing:
Citing byThom.com: "I expect to
see no more than two DSLRs launched in the remainder of 2013: the D400
and the D4x. The D4x seems to be almost a lock, with really only the
timing and the sensor choice being unknown at this point."
If Nikon happens to make another big MP camera it would definitely put a big pressure on Canon.
So I think this rumour is quite substantiated.