We are considering having the database available in off-line mode, but this will probably void one of the most apparent benefit of XPOI: the availability of a constantly updated database, without having to mantain the updates yourself.
To give you an idea of the update speed, this are the recent changes:http://www.geonames.org/recent-changes.html
And, by "recent", I mean in the last couple of HOURS.
So, I don't know how many users would like to download the database as frequently as needed to keep it reasonably update with Geonames.
Of course, if we started to notice a significant increase of the frequency of downtimes on the Geonames server, we'll take into serious consideration the option of adding an offline mode with a local database but, as long as it runs reasonably well, we'll like the idea of having it constantly updated, because this means better quality data.
One thing it's sure: in case the Geonames server would eventually cease, we WILL implement an offline database: there's now way we'll left users that bought XPOI without any chance to use it.
The next release, that will be out very soon, hopefully this week, will already introduce some offline capabilities, by adding FSX Navaids and Intersections to be displayed as POIs