These are pretty optimistic predictions which is far from reality. If I remember well last time around, he was scared and bowling wide outside off at seventh stumps to a mediocre test batter and a bowling all rounder, Jos Buttler and Chris Woakes respectively.
Once he picks 400 wickets sure then you can talk. At present, his SENA record is poor. In Shaheen's thread also, people have hyped him as next ATG but when someone quoted those numbers, posters over here started talking about his age.
My argument for 400 wickets benchmark being set as pretty high is based on the fact that barring Wasim Akram and Kapil Dev, no Asian fast bowler has picked that many wickets. So, the benchmark is lower for Asian pacers. In Asia, spinners play lead role while pacers take a back seat although Bumrah has a fi-fer there also but he won't get to pick that many wickets in Asia.
Another way of understanding this is say, we compare an Asian spinner to an England or Australian spinner. Harbhajan for example has 400+ test wickets while Swann had 250 odd wickets. But clearly, Swann was a better spinner and it is not possible for him to pick as many wickets as Harbhajan would because Harbhajan played on dustbowls while Swann played on English wickets.