xo6 will eventually be taken offline so you can delete that information from your ftp client, but until we know all accounts work properly on the new servers it will likely remain up, and it could be wise to not delete anything on that server on your own at least until you confirmed everything works properly.
As long as you use the new hostname, and have your domains updated to use the new IP you should be good to go.
198.91.81.15 is the final IP for x15.x10hosting.com.