Tough call. Replicating the 390k the Switch sold during AC's release week is going to be hard. That was already by far the single largest non-holiday week ever for any system ever in Japan, and one of the best single weeks ever overall. However, Monster Hunter is a definite system-seller in Japan, and Rise is clearly going to be by far the most popular third-party game ever on the Switch. MH World drove the PS4 to 140k the week of its release, the second-best week ever for the PS4 after launch week (MHW was also the PS4's best-selling game ever in Japan). MH4 drove the 3DS to 276k the week of its release, making that the third-best non-holiday week and eighth-best overall week ever for the 3DS. The Switch should easily sell over 300k next week, but whether it hits 400k could simply be up to stock and the impact of the LE MH-themed console (and FWIW, there was a LE AC-themed console last March).
Yeah, it is difficult, which makes it an interesting bet. So far people invested more than double into that it fails to bring back AC numbers, so most people are sceptical about this happening.