That is going to be one long wait.
1D: thirty months
1D MkII: twenty one months
1D MkIIN: fifteen months
1D MkIII: thirty three months
1D MkIV: thirty one months
1DX: eighteen months and counting
I estimate that the replacement will be around the thirty six month mark, so another eighteen months is fine by me. If I get work beforehand that demands the better features of the 1DX then I'll get one, but at the moment I am content to wait. I will not buy a lower pixel count than I have unless there is an overwhelming need for me to, on the other hand I have no interest in a very high MP camera.
Don't forget many of these tools are bought by companies on buying cycles, Canon needs to keep renewing their products to keep these big buyers buying, if there is nothing new for them on the 36 month mark they just won't renew, they will just keep their old cameras until a newer overdue model is released.
Canon might like to think they have drew a line in the sand saying the 1DX replaced the 1Ds MkIII, but they fooled nobody, certainly no 1Ds MkIII owners. They will come out with a high MP camera that will be the logical 1Ds replacement, then the 1DX will fall back to being the higher turnover pro "sports" camera.