We're told that we shouldn't expect an EOS-1D X replacement until early 2016. While the announcement could come this year. The source said it may depend on what Nikon does in regards to a D5 announcement as well as getting the new sensor and DIGIC 7 ready.
2016 is an Olympic year, so we definitely expect a new flagship DSLR by then.
As Canon has said, they won't be replacing cameras until there is enough technology improvements to warrant a new product.