Ain't going to happen, my friend.
Seriously though, you pose a valid and interesting question. Where does a new god get his/her followers from?
In the past the followers of a new god were the people who helped him to become a god. However, now that there are many many more players, I do not see why the new god should not, by agreement with his patron (or the patron of the people concerned) take a couple of his lieutenants as followers, and essentially start from scratch with younger players.
Gods do not need mana. Their essence does depend, to a certain degree on their followers - how much they play, how much they offer, how well they do etc. However, do not forget that we gods do not exist because of you mortals, but rather the other way around.
What concerns me more is whether new gods will feel that they have some right to take over the patronage of their guilds, and even cities. I would think that that is a more difficult question to answer.
However, in the weeks following the 23rd October, we shall find out just how the new