It's not old for some of us. I quit a month or so in to GoD. This is a perfect chance to pick it back up and learn the new zones and spells as I level along side everyone else.
I seriously doubt it will stay open for 3 months, Mata will be dead in less then a month... would not be surprised if the whole thing was over by the end of the second week.
They will not close the server down after it's defeated. It will stay open throughout the originally stated period, that's why there are prizes beyond just the "first" to beat the content.