I think it is too early to pop open the champagne. While Dutton will be gone from DHA, the ruling party will still have to appeal to its core of conservative supporters, so I am sure that nothing will change with immigration numbers. But it should not get worse for now.
Also, this is probably just the start of the end for Turnbull. It's just a matter of time before there will be another leadership challenge. Earliest 2 to 3 months down the road - definitely before the polls. If Dutton gets in then, expect things to get worse then.