Calgary with that offer sheet is probably what messed that up (they massively priced him way above what Colorado wanted to pay, but Colorado didn't want to lose him for nothing and thus matched---thankfully, he has justified his high salary even if he had to be traded before he reached UFA status---before that, fearing another offer sheet, the Avs took ROR to arbitration). That said, I honestly believe that Buffalo would be crazy not to eventually put the C on his sweater. He is truly a hard worker with a great all-around game.
Also of note---Ryan O'Reilly was a second-round pick, but made the NHL for good in his draft year, at the age of 18. How many 18-year olds have played a full season in the league who weren't first-round picks?