Jon, who has five full caps, will join Hull when his current contract with Borders expires at the end of the month.
"I enjoyed rugby union for five years," he said. "I've played at the highest level and I've done everything there is to do.
"It's definitely a new challenge and something different but I'm sure after three or four weeks I should pick it up fairly quickly.
"It's mainly positional differences and also about work-rate. In league you have no rest at line-outs. The way I play, however, will be suited to league. I'm also looking forward to playing in drier and faster conditions over the summer.
"I am ambitious to play in Super League and so are Hull Kingston Rovers. I'm sure together we'll do well."
Middlesbrough-born Jon made his Scotland debut against the United States in the autumn of 2000 and joined the Borders from Glasgow at the beginning of this season.
Borders chief executive Alastair Cranston said: "Jon is the epitome of the professional player. He is dedicated to his sport. We wish him well at Hull KR."
Jon's Glasgow-born father Jim, who was involved in the contract negotiations, admitted the move was prompted by uncertainty over the future of professional rugby in Scotland.
He said: "We don't know if the Borders will be on the map next season and this was a factor in deciding on the move to Hull KR. This is a new challenge for Jon and I think it will be good for him."