I don't see him getting 70 wickets to reach 400.
Realistically, if we consider that he'll play only this WTC cycle, he has 8 Home Tests excluding the current one and 2 Tests in SL i.e 10 Tests to get nearly 70 Wickets. I don't think he'll make the playing XI in NZ. Even if he does, he won't pick more than 4 Wickets in those 2 Tests.
So, 10 Tests for 65-70 Wickets. Not happening.