1) You do realize he's much further ahead this year than last? Seems to have made it to another level. 47 low would not be a surprise this year. What about going from 48.84 secs in 2016 to 48.22 supports your claim 47 low would not surprise? Other than his whiteness, of course?
He was doing a lot of other events and don't think he focused on the 400 hurdles til recently. He improved his 400 flat speed a ton from 2016 to 2017 and that was probably a good indicator for the hurdles. I don't think he got the technical aspect of the hurdles in 2017 but should have been even high 47s last year.
The biggest mistake that people make about the 400H is that they assume the technical aspect of the event will just "come" to you at some point or another. Some (even most) athletes will never get it right. Remember that Edwin Moses is the only person in the history of the event who has ever been able to consistently 13-step a race. Even look at a Kerron Clement, arguably a more physically gifted athlete than Moses, who has never managed to run faster nor been anywhere close to as consistent.
This 34.2 WR is a moot point, hardly any professional hurdler has ever even attempted the race. When I was a collegiate 400 hurdler, we would run sub-36 in reps over the first 8 as a speed workout. Warholm is a good athlete in a time in the event where good is good enough to win a major championship. We will just have to see what he does, there is nothing about him that "screams" sub-48, and theres certainly less that screams 47-low. Maybe he can, maybe he can't. Time will tell.