The reveal event is in 3 days. After that, we're looking at a minimum of about 18 months before first deliveries.
I don't think Tesla will need much in the way of teasers to generate sustained interest. As things stand, there's already a niche industry of car paparazzi that sells spy photos to the major industry publications. We'll have plenty of camo'd prototypes to drool over as the Model 3 gets closer to production.
Get ready for endless speculation on how the Model 3 design will evolve, both inside and outside.