Got this from the FreeForums folks today:
Update 9/15:
We will be replacing the web servers sometime between the 21st-25th of this month. This will be seamless and no one will even know it's going on. We will update here with progress
We will also be also replacing all the database servers starting this Sunday (20th). This will include moving hundreds of gigabytes of data over the network to the new servers. Downtime per forum may be up to 10 hours, or as little as 20minutes. We will give everyone a 48 hour warning and say the estimated downtime this weekend. Keep in mind all downtime will be early morning PST to minimize the inconvenience.
We expect to give another update by Friday.
Update: 9/19
We now have a brand new web and a new database server in our hands and will start testing tonight/tomorrow. We expect to be able to provide downtime numbers on Monday for the transfers happening mid next week.
As per company policy we will provide 24 hours warning for any downtime over one hour, so look out for a post in here and in your admin warning box shortly.