First, I'll answer the most important question. No, I don't think the game is dying. I have three long-term worlds and all roll within hours if not minutes. We have waitlists and limited openings each season. They are good, competitive worlds and people want in.
Now, for the ugly part. Some worlds are dying. It's natural and likely self-inflicted. WifS has taken away our ability to "check" worlds for unbalanced results, horrible trades or general apathy. So all we have to look at is number of openings. If I see a private world with 7 openings, I'm thinking the worst. Incentives won't bring me in. The game costs $8 a month. More important to me would be the number of seasons I'll play in 2016. Will I get 3-4 seasons or 1-2 because of slow rollover? There's nothing worse than waiting to play. If you're good, you want to get right back at it. If you're bad, you want to get that rebuild going. If I think it's going to be 2018 before I get a playoff appearance because of slow rolls, well, that's too long.
FWIW, I commish two worlds and will admit that there is less interest. I have waiting lists but they're not as long as they used to be. In addition, interest comes later rather than early. If I start a thread with 30 days left in the season, no one inquires. But, when there's a week left, people start showing up. And I think that comes from the desire to "play now".
Finally, I think the solution is to allow varying world sizes. 20, 24, 28 and 32. Your 7 openings is the worst, you'd contract to 28 and still have three while, if you had 8 openings, you'd go to 24 and play tomorrow. Once a world gets to 20 and sits for a month, it is done. I don't know how much programming would be involved but no one would have more than 3 openings the very moment it was accomplished. That said, there would be massive ******** when that 110 win team drops to 92 because there are no weak sisters to beat up but you gotta break some eggs to make an omelet.