This is like when a poor hitter goes on a couple of month hot streak with a bunch of bloop hits and seeing eye singles and everyone thinks they've figured it out. Or when a guy who gets a few key hits in clutch situations and he's deemed to be a "clutch hitter." He's playing with a .500 BABIP. He's the closer racking up saves by loading the bases, giving up a run or two, but getting a luck out to end the game. Winning in the way they are now is not sustainable.
The guy is a good athlete and it's entirely possible that he'll get better. But if he plays like he's been playing as a QB, he will regress to the mean and it won't be pretty. Either that, or he will significantly improve, which isn't out of the realm of possibility. But as soon as they lose a couple of games, you won't hear players talking about his motivational speeches and how he's making the defense play better. Wait until they lose a couple where the defense keeps the opponent to 10 points (like almost happened today).
And don't kid yourself, Elway knows this. You think he wouldn't take a QB in the draft this year if a good one is available when the Broncos pick? This is a deep QB draft, so it wouldn't surprise me.