"You are going to drop the plate."
Translation:Du kommer til å miste tallerkenen.
Yes. Skal means it is planned. For things that can't be planned (like how you're going to feel, for example), you have to use vil or kommer til å.
For example: Jeg skal reise i morgen. Jeg kommer til å savne deg. (I am going to travel tomorrow. I will miss you.)
The only context I can imagine "Du skal miste tallerkenen" would make sense in is if it were a script for a play or something and in that part of the script you were supposed to drop the plate. Although the script probably wouldn't put it in future tense. But the director might say what's going to happen as he describes your part in the scene.