That doesn't mean the title will be going down without one heckuva fight! According to Wrath of Heroes' Facebook page, the developers are spending the last few hours in battle with the players. The team has also added a chance for killers to transform into vampire chickens or bloodthirsters.
If you're just now finding out about the sunset and want more information, check out EA's FAQ on the closure.
[Thanks to Adam for the tip!]