That's a little aggressive. I would expect them to consider keeping Morin and Parker (I think they are both controlled?). Velasquez isn't going anywhere before the Rule V and may even be ahead of Pivetta at this point.
Hard to know for sure how they will proceed with Franco, but especially with Hernandez. I can't see him just being non-tendered and a trade might not happen before Rule V.
Don't know that Irvin and Knapp are guaranteed gone before Rule V either.
But, they also lose Hunter and Neshek and Dickerson.
I don't think it's about the 40-man space, I think it's about rushing Howard when he hasn't even touched the major league ball and starting his service clock for almost no reason.
Plus (as julio noted) he's going to the AFL which begins September 18. Doubt that plan is changing for a kid who started the year injured. (I assume if he gets called up he wouldn't even be allowed to play in that league, never mind that he'd be unavailable for a while.)