For sure they won't cut off already flashed users, That would mean huge losses for them. Now the rumor about them shutting down Metro Flash and Houdini seems to be more real each time, and when you think about it, It makes sense. They want users to spend money on their phones! And I have to admit they have been making an effort to take out pretty good phones, they even have a dual core phone now!
But hopefully they won't shutdown Houdini, as I know plenty of people that make a living flashing phones.