Gear becoming obsolete after three months would be bad, but that is a misrepresentation of Yoshida's post.

A new challenge every three months where the hardcore players get to assert their dominance and be the first to show off the new loot is a good thing. Even with new gear coming out regularly, it might be a long while before something specific like the best-in-class tanking rings are made obsolete.

Content can have worthwhile rewards other than gear. Access to new areas, like Sky and Sea, or new weaponskills like those obtained from Nyzul Isle assault are examples from FFXI.

So there is potentially a lot of "stuff" to obtain, not all of it gear. A certain percentage of that stuff should become obsolete every three months or so.