The serviceable life for a 1D is definitely more than ~5.5 years...
Maybe
- The sales of R1 is so overwhelming that everyone has replaced their 1DX
- Canon is forcing 1DX owners to upgrade when/if their 1DX breaks down which also doesn't sound Canon-ish
- Some components are now impossible to get at a reasonable cost so Canon has made it discontinued across some (all) Canon regions
The latter makes more sense than the situation for 5Div.
When Canon discontinues a model they continue supporting it for at least seven years. They hold enough repair parts in reserve that they estimate will last for at least seven years. Some of these come from unsold units returned by dealers when it has been discontinued.
The last time I remember a lens dropping from the repair support list sooner than seven years after it was discontinued was the EF 200mm f/1.8 L because they ran out of parts for it.
The EF 200mm f/1.8 L was introduced in 1988 and discontinued in 2004 or 2005 (Canon never makes an official announcement, they just quietly remove items from their catalog) without an immediate replacement. It was during the period when Canon was eliminating lenses which used lead in the manufacturing process. Only around 8,000 were ever produced. The last known date codes indicate the last production run was in 1998. Lens owners began reporting Canon returned their lenses needing AF motors replaced unrepaired as early as 2006, two years before the EF 200mm f/2 L IS was introduced. By 2007 it was removed from the CPS support list in the U.S.
Since it is a focus-by-wire lens, it can't even be manually focused without an AF motor. Third party repair businesses started reporting they could no longer order the AF motor from Canon shortly after the lens was removed from Canon's catalog.
The EF 200mm f/1.8 L used the same AF motor as the EF 1200mm f/5.6 L (1993-?: less than 100 ever made and more likely around 20 - only three have ever been offered on the used market), EF 300mm f/2.8 L (1987-1999), EF 400mm f/2.8 L (1991-1996), EF 500mm f/4.5 L (1992-1999), and EF 600mm f/4 L (1988-1999). Other than the special order 1200/5.6, which was offered through 2005, all of the other lenses which used the same USM part number for focus-by-wire were discontinued by 1999 and replaced by IS versions which were not focus-by-wire and used other part numbers for the USM. It's been theorized that Canon used up all their reserve of that AF motor on the lenses that were discontinued in the late 1990s.