Based on the fact that the new Project Loveday commercial competition is set to run until May 8, with the winner being chosen after May 22, we may have a guess as to what the assumed grand prize will be.
The Tesla website states:
Grand Prize Winner (1): The Entrant with the top winning Submission will be invited to and introduced at a future Tesla product launch event.
On or about May 29, 2017, the Grand Prize Winner will be sent an email notification with instructions on how to claim the prize. The prize must be claimed by June 2, 2017.
What might Tesla be planning for June 2nd (or thereabouts), and why might the winner have to act so fast?
Likely Model 3, Part 3 right? One would assume that that's the only substantial launch event that Tesla would be planning for the immediate future. There wouldn't be a better event to invite and introduce the winner to, and the event would present the perfect opportunity for Tesla to "air" the winning commercial, due to the wide level of press coverage, and the huge audience.
Perhaps Tesla picked June 2nd to give the winner a bit of time to make travel arrangements, once the prize is claimed and details are divulged.
Obviously, "Model 3 Part 3" will have to happen within a reasonable time around that date if production is to begin this July.