Yes it sure is…
Canon showed the new X against the old road maps of D and Ds on its own plot halfway between the two. So it seems they are not intending to do an Xs.
Yes, if one reads what Canon actually says and trusts them not to be outright lying, this is clearly the case. And if you think that Canon knows its business far better than us forum pundits, this suggests that Canon has judged that there is no longer a sufficient market for the combination of a higher resolution, medium format challenging "tripod camera" with the EOS-1 class body, with the bulk and cost of its extremely rugged body, integrated vertical grip, very high frame rate etc.: the 5D, other less expensive 35mm format DSLRs and more affordable MF options have shrunk that market considerably. Instead, I would infer from Canon's actions that the EOS-1 class body sells primarily for PJ, sports and such, as it was with film, and for that, the trade-offs between high frame rate and higher resolution caps out at 18MP, according to Canon and its current technological limits.
But this does not have to mean that there will be nothing better than the current 5D body for resolution beyond 18MP. Maybe the 5D line will move up in body specs, with a better VF for example, now that this would not eat into the 1Ds market, or maybe an additional intermediate grade of body wil be added, heir to the EOS-3 or F100 film cameras. Such a body could be priced at half as much as the 1Ds models were, so two of these instead of one 1Ds should cover most "field reliability" needs (and reduce lens swapping of course). But maybe Bernard can comment: he seems very experienced at doing high res. photography in rough conditions.