There was a 40K in the past and you got two ninjas. However, since the amount is quite high, it seems that the majority of people don't like it.

Hmm.

The possibility is there but I cannot give you exact information about when it will happen. Even us in the staff team has no idea about the Fukurokumaru's Deal Milestone set for the cycle of the event. The best way you can do is to find out if there's a special occasion in that month and look around the Forum or Discord for the player's discussion about it. Usually, if there's a special event, the Fukurokumaru's Deal is better but at the cost of a higher milestone than the regular week cycles.