WWE released their PPV schedule for 2018 and it drops the number of PPVs down to 14 from 16 in 2017.
The reason for the drop was that WWE started doing PPVs more often after the brand split and WWE Network numbers barely changed, according to the Wrestling Observer Newsletter. WWE just had the added expense of another PPV, though they did make up for some of it with ticket sales. The Observer also pointed out that they felt that the interest level in the smaller PPVs was not very strong, particularly on the SmackDown side.
As mentioned in the schedule, Money in the Bank will become a dual-brand show. This likely means that there would be at least two Money in the Bank matches, and possibly even four, though we’ll have to see if four of the same gimmick match on one show would get tiring. The Wrestling Observer says that the idea right now is two Money in the Bank matches, but the possibility of four is also being considered. It would seem to make the most sense to me to have a dual-branded men’s match and dual-branded women’s match rather than four separate matches. It was also noted that the idea of a third match with tag team competitors has been floated.