Ryuutaro was one step short of telling Hayato he did not need those reassurances, but he didn't. Because he really did and believing Hayato did help him a great deal right now.
He just remained close to Hayato, holding on to him. They'd be out of here soon, he wouldn't have to spend much time as a prisoner again. Not again.

But then the machine opened and Ryuutaro raised his head to look inside as well. So that was what he'd look like. What he'd become and who he'd stay with.
He was considerably less shocked than Gokudera though. Even if this was the farthest and most real look into the future he had, he still was used to it.
This was just proof of what was his fate and what ought to happen.
His look wandered from his older self to the older Hayato, curiously for a moment. This was the man he was going to see the boy next to him grow into. A fascinating thought, indeed.
He looked up at Hayato and for a short moment he was smiling.
"Looks like interesting times to come", he said silently, not really expecting any sort of answer.