I was thinking about J.R.'s line about it being his greatest plan ever (or something close to that)
Perhaps J.R. learned he was dying of something inoperable, and arranged to have himself killed, and fabricated evidence to link his death to Cliff Barnes.
And Jon Ross learns of it, and instead blackmails Pamela into supporting him at Ewing Energies so Cliff isn't arrested.
I could just see J.R. taking one last shot at Cliff, and Jon Ross messing that up for his own interests.
Perhaps J.R. learned he was dying of something inoperable, and arranged to have himself killed, and fabricated evidence to link his death to Cliff Barnes.
And Jon Ross learns of it, and instead blackmails Pamela into supporting him at Ewing Energies so Cliff isn't arrested.
I could just see J.R. taking one last shot at Cliff, and Jon Ross messing that up for his own interests.