Trailer

Not necessarily they will release a trailer, sometimes before Cannes studios just drop couple of clips, and depending on the festival's reception, they release more marketing and set up the date for theatrical release.

But I hope to see trailer soon too to be honest

I don't think so...

the Cannes opening ceremony reel showed some footage from the teaser trailer

see at 25 min 29 sec

http://www.festival-cannes.com/en/actualites/videos/opening-ceremony-of-the-69th-festival-de-cannes-1

dialogue less same as the teaser trailer for The Company Men (2010)