Will my retainer still keep my teeth in place, even though my tongue thrusts, after braces?

Not likely: Your tongue is a very strong muscle and when you constantly thrust it against your teeth it has the potential to move them, even with your retainer. Of course, the movement will be less than it would be without your retainer but you can still expect some movement. It's best to work on controlling that habit.

It might: But it will only work when you are wearing it. When it is not in your mouth, the habit will put pressure on the teeth. Work on breaking that habit by talking to your orthodontist.

Can be problem: There is research to show that is as many as 97% of patients with muscle function problems, normalize the environment (straighten the teeth) and muscle function normalizes. Have your occlusion corrected, wear your retainers as directed, and you may be ok. If not, permanent retention may be required.