Not sure that the 50th anniversary is going to be a selling point to ordinary moviegoers... And the fans will go anyway, so...
The 50th anniversary guarantees lots of extra free publicity. Newspapers, magazines, websites and TV shows doing retrospectives. Bookshops doing displays.
The 20th anniversary was a Really Big Deal. ST IV rode it well. And the general public responded.
Well, free publicity can't hurt, and might help, that's true. I was only concerned about the producers of the next movie actually harping on the 50th as a selling point to see the new installment, which could backfire something awful. Let the newspapers, magazines, etc. do the heavy lifting in that particular regard...