Its not good business sense to erase characters from inactive accounts. I have played a bunch (and when say a bunch I mean a BUNCH) of MMOs over the years and never have I seen a company purge inactive characters. There is always a chance that said person will come back. If his characters are gone he wont be here long.
For example I used to play ultima online and quit around Jan of 2001. I saw they had a welcome back weekend I logged in and all my characters were there. Thats 9 years inactive and they didnt purge my guys. I think you are safe.
Your article says only two games out of all MMOs ever created have deleted inactive characters. Also even funcom is only deleting characters level 20 or under (you cannot even leave the tutorial island as far as I recall until level 20). So basically they are saying that they are deleting characters people got sick of and never even finished the tutorial with.