Actually Pentax makes DSLRs and maybe some some day soon they will be the only DSLR manufacturer.DSLRs comprise over 40% of the ILC market. Only Canon and Nikon make DSLRs, and Canon’s market share is somewhere over triple Nikon’s, so most of the DSLRs being sold are Canon.
So what you’re saying is that you can’t imagine Canon making any development investment what is probably ~30% of the total ILC market. Are you sure that makes sense?
What doesn't make sense is for a maufacturer to have two lines of full frame lens mounts competing with each other for the same market. Sony abandoned their DSLR mount and I fully expect Canon and Nikon to do the same - I have seen no indication that either company is continuing to develop their DSLR lines.