From the September 6th post on the movie's Facebook page :
QUESTION AND ANSWER TIME! For the creator of the Matador universe, Steve Perry.
SCOTT NICHOLSON KURLAND: How real is the 97 Steps? Fictionalized silat?
STEVE PERRY: It was completely made up when I started the books. A blend of aikido, kung-fu, tai chi, wu shu, ballet and gymnastics. Later, when I happened across silat and saw the parallels -- patterns on the ground, black steel, and the efficacy of the fighting form, I was surprised. A lot of what I thought I made up was already out there. The Musashi Flex is pretty much pure Silat Sera Plinck.
Silat Sera Plinck is the variant of Pencak Silat Sera taught by Guru Stevan Plinck.
In the source you reference, Steve Perry admits to having practiced different martial arts to some degree. He explains that it allowed him to basically create a fake martial art that was realistic enough, yet 100% fake.
I got a fair amount of fan mail from martial artists who saw their art
in mine because I was careful not to get too specific in the
description of the stuff.
It is only years later, when he encountered Silat, that he realized how similar it was to his "fake" art. There were some differences, notably in the footwork, but it was close enough that Perry decided that Silat Sera would be the influence of Sumito for future novels of the series.
The most recent novel in the series, silat Sera is the core of the art
of sumito, principles, philosophy, technique.
When the movie comes out, Sumito will thus most likely be depicted using Silat Sera Plinck moves. The 97 steps will most likely be basic sequences used in training, maybe extracted from the style's different forms and assembled in different ways.
If you want to see what it looks like beforehand, the Resonant-video YouTube channel has some trailers from Guru Stevan Plinck's seminars and workshops DVDs. Here is Guru Plinck demonstrating a Serak form 25 years ago. And for what it's worth, the Fight Quest series had an episode featuring Pencak Silat, which should provide a decent approximation.
There are countless videos available on YouTube featuring different styles and variants of Silat, if you wish to see more of the style in action. Most schools are descended from family styles, however, and they might differ to some extent from the style Steve Perry practices and uses as influence for Sumito.