Martin Kerstein has written a new blog article stating that there will be a mandatory password change coming soon. As mentioned in a previous article by Mike O'Brien, ArenaNet has created a blacklist of passwords that have been previously used by hackers for new accounts. Since the system has been rather successful for newly created accounts, they will be forcing existing account owners to change their old passwords.
If you still have the red banner at the top of your launcher, it means your password precedes the blacklist and you will eventually be forced to change it. You can go ahead and change your password at your leisure, but if you wait, you will be forced to change it on February 7th.