As I said in the title, I wish to know if there is a way to know the monster of the HoH before the weekend rolls around, and if so, how.
The upcoming Hall of Heroes will be announced in the news (under notices) about a week before the HoH opens up.
There is no other reliable way to tell what monster will be up next.
The only thing we know in advance is the element of the upcoming HoH monster, because it has a fixed rotation (special events (like Halloween) excluded):
Wind -> Water -> Fire -> Light -> Dark
Since the last monster was a Magic Knight (Wind) we can safely assume a Water type will be up next in December 2017. Everything else is speculative.