Any posts made after the backup is taken will not be migrated to the new site.
This is because we need to do some massaging data and config setup on the new site, but we don't have a way of porting just posts over after that's done (well, we maybe technically could, but it'd be way too much...
REMINDER!
This weekend we will begin the migration process of bringing us over to the new version of vBulletin.
I'll be beginning a backup and export of the current site this Friday (Oct 3). This may result in some downtime/slowness. I don't expect this to take too long, but the whole weekend...