OP: Yes, it should show your last night. Whether it is at midnight or earlier will probably depend on how popular it is expected to be and what land theatres are doing.
We were on the Dream when Star Wars The Force Awakens premiered. It was obviously anticipated to be very popular.
On land, the official premier was Friday (the day we got off the ship). However, SOME land theatres were allowed to start showings as early as 7 pm on Thursday. Those that didn't start Thursday evening generally started their showings at midnight between Thursday and Friday and then all through Friday etc.
On the Dream, they had many announcements and flyers in every room letting everyone know how the showings would go and reassuring everyone that everyone who wanted to see it would be able to.
They showed it in both theatres -- one was 3D one was normal.
For the first two showings 7 and I think it was 1015, people were assigned to the showing by their dinner time.
So, if you had early dining, you went to the 7 pm show. If you had late dining, you went to the 1015 show.
They changed the late dinner time on Thursday to 800 instead of 815 to facilitate the movie. They also moved the normal "show" (a variety or ventriliquist or something; we didn't go to it) for that night to earlier in the day.
The servers of course knew and made efforts to ensure everyone would be done in time to go to the movie.
Once those two showings were done, it was free for all. They had another showing around midnight (both theatres IIRC), then one at 5 am (yep, on debarkation day... so watch the movie then off the ship) (I think for that one only one theatre).
There was plenty of SW merchandise to purchase including
DCL themed stuff and items unique to the PremEar. For example, there were special pins one could buy -- a day before they released you went to a specific shop and told them how many you wanted -- they had a list of all the staterooms and you were allowed up to two per person. You then got a "receipt" to bring back the next day to claim them. Postcards, magnets, clothing, accessories, etc etc.
SW