Von Miller has just tweeted:
Seeing reports abt 4 game susp. I know I did nothing wrong. I'm sure this'll be resolved fairly. Disapp. Broncos have 2 open camp like this.— Von Miller (@MillerLite40) July 22, 2013
Not that you would need that translated, but he is saying, "Seeing reports about [a] four game suspension. I know [that] I did nothing wrong. I'm sure this [will] be resolved fairly. [I am] disappointed [the] Broncos have to open [training] camp like this."
So there you have it, there should be an official statement very soon. We will update you here when we have it.
UPDATE (7/22 2:30 PM MTN):
Of course it was over performance enhancing drugs, the Seattle Seahawks cornerback Richard Sherman not being suspended last season in a rare victory against the NFL creates precedence for no suspension.
If Miller is suspended, the Denver Broncos could pursue and recover $860,000 of Von Miller's original signing bonus.