I think the March 2013 date is a typo... Should be March 2012. If you look all the way at the bottom of the PDF, it says:

・April 2012 –Version 2.0 client system complete
-Commence porting of current game content to version 2.0 client

Don't think they'd start porting data a year before the development of it was done. Everything in that PDF has 2012 stamped all over it.

And yes, migrating the data over could indeed take a month. I've worked on much smaller scale projects where data conversion took a full day (10+ hours). Don't forget, they're not just copying a file from one machine to another.. The data needs to be converted to fit whatever new data structure they have on the new systems.

I'm like the majority here, expecting downtime late this year, back up early next.. A welcomed break to play some other games that have been piling up.