Not that he killed them, not yet, as that hasn't been proven in court. We do know he did many of the things he has been accused of... he has admitted to them in court and lying about it, for any reason, would be felony perjury. It still stands to be proven that he actually killed any dogs himself, and we'll have to see if that ever gets a day in court. I think it will as his plea won't satisfy the people that want to see him punished.
The Falcons are going after $22mil of his bonus money now... so, in the grand scheme of things, being banished from the NFL, losing all of his future earnings, and most of his past earnings is a much larger punishment than going to jail for 18 months.