[ArchonShiva]

I have zero doubt that DFRPG will be played a decade from now, even if SJG terminates the line tomorrow. Now, is there a way to increase that play and make SJG money?

To me and those I can see using it, the upsides to DFRPG are:
1. Self-contained: It requires a limited number of books to have “complete” rules and options.
2. Curated: Every rule, template, and item has been looked over by a single intelligence, in light of lots of feedback.
This is like the second coming of the GURPS Compendiums, which I still think of as the single best GURPS release in history.

What should happen now, if SJG is to make money from DFRPG:
Buying Adventurers, Exploits and Spells must be an option for players. If this is somehow more viable, a single book containing Adventurers and those bits of Exploits that players need (aka Player’s Handbook without spells) would be great, but I wouldn’t count on it.
GMs must additionally be able to buy Monsters (and the rest of Exploits, if that is a thing).
Without essential books available, there are no new games, and few new players. Either SJG makes that gamble or they don’t, but it’s a baseline requirement for anything else to happen.
PDF-only *is* a option, but it basically means tabletop is out: DFRPG mostly becomes an online-only game, except for the lucky few who have the books, or the resources to have them made.
Magic Items and Traps are nice, but home-printed PDFs will do just fine.

If the above happens, then I think there are three additional paths worth exploring:
1. Third-party adventures: Open up publishing adventures to anyone who cares to. Don’t go full OGL, but encourage people to make money from whatever adventure in whatever format. They will have an interest in you selling your books, and become your ambassador; they will create the support that the game needs. Either say no to new templates, spells and non-unique items, or assign quotas (5% of word count for new spells and stuff, to make sure they strictly remain adventures.)
2. Favor VTT integration: DFRPG being separate from GURPS is a boon here, as it allows taking some risks with licensing without selling out the main game.
3. If and when the thresholds are met, publish new full-sized books, obviously PDF at first, which grow the game at a slow and steady pace, stay true to the game’s style, and keep everyone on the same page. Adventurers II, for example, with some of the more reasonable new professions, and a few more races, multi-classing lenses, and maybe new equipment options. No all-out crazy “what did I just buy?” stuff like DF. New books should basically be must-buys or not happen at all, and the total number should be few. If this step is never reached, so be it; there’s always DF, and the DFRPG stands solidly anyway.