Pretty sure that if offered a new mode for your favorite pinball game....you wouldn't be able to get your cash out quick enough. Take it from me, games like Ghostbusters are only half-finished. A few extra hours of code and you can add so much more fun. Same for any pinball game.
I'm pretty sure they just want subscribers to their Insider service, so any DLC will most likely be free and exclusive. Which means, every man and his dog who owns a Stern pinball machine will sign up.....eventually. Some will bitch and moan for a while, but you will all sign up. They're counting on it.