Hard to believe that anything can top Animal Crossing on Switch, but still possible if you look at the 3DS. I'd say "no", but there's still a 30 % chance imo that Monster Hunter can beat AC in launch week in Japan. I mean, the demand for the Monster Hunter demo already crashed the UK Nintendo eShop , so if people are hyped in the UK â€“ they surely are in Japan, too ^^
It's talking about hardware sales, not if Monster Hunter can beat Animal Crossing's first week of sales (sorry if you already know this, but your post sounds to me like software sales analysis).
In that case, a lot of it is just up to how much saturation there is in Switch purchases (doesn't seem like there's many, seems like the system still has a lot of life in it) and how much stock there is for Monster Hunter Rise's release. There is certainly a factor of how attractive the software is, but considering both series have had similar first week sales in the past (I actually didn't realize MH4 was so close to ACNH) I don't think it factors that much into the result. Especially because software backlogs are a thing, there's a lot of software in 2020 that might help convince people who were waiting to get a Switch to get it alongside the release of MHR just being a huge thing in Japan.