Anybody who plays retail will notice that as of November 11th, you will need a Battle.net account to play World of Warcraft (retail). What people don't realize is what blizzard has in store for private servers. Read the quote from the Battle.net FAQ below...
This says that anybody without a Battle.net account will not be able to access the game. This means that without a b.net account, you will get an error at the loginscreen. Why is this a problem? The battle.net realmlist is built into the client! (<- not changeable)After November 11, 2009, you won’t be able to log in to the game unless you merge your account with a Battle.net account. You will need to log in using your Battle.net account username (your email address) and password.
To prove my point above, go change your realmlist to one of a private server... if you log in without an email it will take you to the private server. If you log in with an email, it will take you to retail wow. The realmlist.wtf will no longer be needed after November 11th, thus private servers will no longer be able to go past the current patch.
Hopefully somebody can prove me wrong, but from what i've experienced so far with the new battle.net system, it does not look good.