I realize the conventional wisdom is that doing much of anything creative by committee, or even in a team, is a poor idea, especially when it comes to RPGs, but I've been wondering…
What if a dozen or so people got together and everyone who had an idea (the more out-of-the-box the better, though creative, interesting takes on classic/traditional-style settings are allowed) for a setting drew lots to decide who's idea they would work on first. Then they spend six months fleshing out the setting together, improving the format, making art, writing gazetteers and bestiaries and porting them into 3-5 different systems to be released simultaneously.
And then what if they spent the next six months writing adventures. There would be some leeway for each person to contribute during the setting creation phase, but the real license to go their own way would come here, with all kinds of adventures, varying in tone, style (sand-boxy hooks and relationships, one-shots, adventure paths, etc.), seriousness, whatever.
Then, after those adventures have been released, we have a reasonably well developed setting, complete with maybe 20-30 adventures. That counts as well-supported, I'd say.
Then everyone with an idea for a setting draws lots again and works on fleshing out a new setting for the next six months.
Then, during the six-month adventure-writing phase adventures are allowed to be written for either setting already produced, allowing for continuing support. The added choice, especially as the cycles continue, encourages fresh, exciting, well-done adventures, with more settings hopefully increasing the chance of good ideas occurring to adventure writers.
As this continues, more people join in, allowing for new settings to still have enough adventures written for them and eventually allowing some members to skip the setting-creation cycles sometimes and write adventures for 18 months straight.