Dropping users with the 10's of millions of EF-S lenses would more likely kill Canon.
The APS-C / EF-s market makes up most of Canon's DSLR sales, and they are eating Nikon and Sony's lunch.
I love APS-H, but I do not see Canon killing off themselves purposely. If low cost FF cameras are actually coming out, our APS-H bodies may be the last of a 20 year run. (My Kodak DCS 460 from 1995).
APS-H was originally made due to lithography limitations, it was te largest senso size that could be made with one pass. The restriction is lifted now, and 12 inch wafers are used instead of 8 in wafers to give better yield.
There really are no compelling reasons to keep churning them out.