Can an absent GM be replaced? (not urgent)

This is not an urgent issue, I am just wondering what the steps are to replace an absent guild master?
He has not logged in at all in the last 3 months.
He's not dead or anything, he just got bored with the game and stopped playing (he's active on facebook and twitter according to a former guild member that knows him).
The current, long standing, guild members have discussed this and decided we will give him until the start of the new year to at least log into the game before proceeding to ask Blizzard to hand it over to an officer that has been in the guild for 4 years and has never taken an extended absence.

We do not know if he plans to come back when cataclysm comes out. He has had no contact with anyone in the guild in the last 3 months.
In the event that he doesn't, we would like to know what the process is to make someone else GM because we would rather not have to leave the guild to create a new one, if that's possible.

I know a lot of people are taking a break before cataclysm, this has been going on for the better part of a year with him logging in only once every few months.