My expertise is in analyses, here's my two cents.
Themes matter to many people. It draws them in. To estimate success, I look first at the theme, but more specifically to a pinball machine's broad or most generic theme, which matters more in overall appeal to people than the detailed aspects of its theme. The more novel the general theme, combined with overall and mass appeal, the more chance for success imo.
FF is a car culture theme in the end (its most basic broad theme). That theme has been done lots. Been done lately too. The mustang pin had at least as much appeal, and better appeal to the older crowd who happen to play more pinball and can afford to buy pinball machines. Sales. Not so good from what I've read. I'd be surprised if FF did better than the mustang pin in sales. Even mustang pin owners say the game is fun. Though it hasn't translated into big sales.
On the other side, TWD is a recent example of a fairly novel and broad theme for a pin. Its adult-oriented zombie theme is fairly unique in pinball (plus monster themes haven't been done for a fair bit of time too). Zombie pop culture has had a big resurgence and is more popular than ever. Tied into a very popular show as well. So all this also checks the boxes for overall and mass appeal. And we see this machine has sold quite well, notably beyond some heavy negative feedback and naysayers in this community. One can go on with other relatively novel broad themes with overall and mass appeal as well, that have had recent success..... WOZ, newer comic book, band pins, etc.
As another pin theme that I think would sell well along these assessment lines (agree or not), I see merit in a Mad Max pin (said it before). The franchise is big, storied and well-reviewed/received. It is now going to be current and relevant again (quite important, as compared to Jaws, for example). The reboot is looking awesome (google for the trailer, and I posted it earlier). It's an apocalypse-themed pin.... not very common, yet with much broad appeal. I see a lot of upside and appeal for this pin imo.
Just some thoughts. By all means discuss.