I think we can debate how much improvement is needed, but we'd both agree that some improvement is expected. If for some reason, he doesn't improve? There's no question that at some point Tua could pressure him for the starting job.
One reason I do not like the idea of a quarterback battle, is I think it could potentially do harm to both involved. I spent some time looking up various stats and what not, and generally speaking quarterbacks improve over time. The instances in which this pattern seems most easily broken was when there ended up being some prolonged/mid-season quarterback battle. Now, sometimes you'd have almost a chicken and the egg question, did they struggle because they got benched or get benched because they struggled? But, the interesting thing is this sometimes seemed to hurt the development of the other quarterback in the battle as well. That's an interesting thing to consider, but I think there's some logic to it.
If a quarterback is the backup, and he knows that's his role, he can kind of settle into it. He can focus on what he needs to do, and develop. The starter likewise can settle into that role. The back and forth, and uncertainty that can bring sometimes seems to be able to throw both quarterbacks off, and cause both to lose some focus and confidence. Obviously, that could impact different players differently, but I think quarterbacks can benefit from certainty more than some other positions.
I'd love that, but man... I'm more expecting people to be complaining about Hurts. He'll be on his third OC for his third game, and all against elite defenses (really making for four straight elite defenses he'll have faced). It's got to be one of the toughest string of games any college quarterback has faced, I'll take an ugly win but I'll be ecstatic if we see Tua in a blowout.