Could the actual front-office of a baseball team know more about the inner workings of its players than some anonymous dude on a fan message board? Absolutely not! 
Of course they might - but even if Bryce right now took out a full-size billboard today that says "I WILL SIGN AN EXTENSION WITH THE NATS IF I MAKE THE CLUB OUT OF SPRING TRAINING," I think Rizzo would be a fool to believe him. The kid's 19 - he has no more idea where he wants to be when he's 25 than any of us did as sophomores in college.
Any decision that stems from the assumption that he's going to sign an extension, regardless of the information that Rizzo does or doesn't have is a fundamentally incredibly risky assumption. Trading a full year of team control on the basis of interpretation of feelings surrounding the mind of a 19 year old is plain foolishness. I'm not saying it's impossible that he might ultimately decide he just loves DC and wants to stay - I'm just saying you don't give away a year of control on the hope that he falls in love.
unless they actually sign him to one, i.e longoria before they let him come up
