Those are just words. JJ wants no part of Cain. Stylistically he's just a bad matchup. A LHW fighter moving up has a good chance against a slow fighter who gasses out ex, couture vs tim sylvia. But in this case Cain is a grinder with excellent wrestling and relentless pressure.
It's a long way away too. JJ fights twice a year, so he probably won't be ready to fight a HW until next Fall.
I'd love to see how he does against bigger fighters though, and would have a tremendous amount of respect for him if he moved up in weight. He's the best fighter in the world imo, and he's shown he has heart when he's in a tough fight but moving up seems out of character.