Both servers will be brought offline at 5:00 a.m. EST on February 26th. The maintenance required to merge the two servers is expected to run for 24 hours, with the usual caveat that it may run longer depending on any issues encountered during the process. Afterwards, players will be able to log in to the new combined server and start welcoming their new neighbors... or start shooting them in their faces for property rights. As we said, general mass hysteria.
[Thanks to David for the tip!]