The Plimlico plumbers and the HMRC marketing case showed it can be challenged to get workers rights. It will kill off contracting as we currently know it and the flexible workforce business likes to retain.
I think in terms of IT roles, companies will just be clever about how contracts are worded now. As long as you can still prove you wouldn't basically be an employee if you weren't operating through a limited company, you'll still be outside IR35. I know quite a few people in public sector contract roles (where these new reforms already apply) that are outside of IR35 because they either supply their own equipment in terms of laptops or software, or they are basically remote workers first who can come in to the office "if required".
My current contract would see me fall outside IR35 even in 2020 I think due to it explicitly stating I don't have to do any kind of company training or inductions, remote working and can work between projects where I see fit as opposed to being told what to work on.
No doubt contracting will change, but I think a lot of the IT jobs will just have cleverly worded contracts. I'm not too worried yet, and I still think this will either get changed or dismissed completely by the time it's due to be enforced. It got voted out last time, although not strictly the same, and there's a lot of uproar about it at the moment so who knows.