This post is just what it says. Looking back at the delay between the final release of "A Shantotto Ascension" and the release of "Visions of Abyssea" in order to guess at how long it may be before we see a new series of content introduced to FFXI. Whether it's more addons or whatever. Here's the breakdown:

*All these dates used are the dates the content went live in the update, not the presale date, or announcement or anything*

A Shantoto Ascension: 11 9 2009
Visions of Abyssea: 6 21 2010
It is 224 days from the start date to the end date.
Or 7 months, 12 days

Heroes of Abyssea: 12 6 2010
Today: 3 11 2011
It is 95 days from the start date to the end date.
Or 3 months, 5 days

By subtracting the current time between the release of Heroes and today, from the total period between the Addon Scenarios and Abyssea we get:
224 - 95 = 129 days worth of difference.

And so, if the past is any rough indication it may now be about 130 more days until some kind of new addon type content goes live. Let's see what happens.