For the past 2 GTA 5 gameplay trailers, there has been no signs of vehicle damage shown in gameplay. There has been vehicle explosions that ending up only blowing out the windows, nothing else.
In gameplay trailer #2, around the 0:54 mark, there was damage shown but many people including myself think it wasn't actual gameplay instead a type of CGI. The online gameplay trailer showed 2 Police cars being blown up by a missile shot from a helicopter.
Don't get me wrong. I think car damage will 100% be in GTA 5 but not the same as GTA 4. By that I mean car deformation. I agree that cars will appear damaged but you won't be able to get a crumpled car like in GTA 4. With all the features being added in GTA 5, it's not hard to understand why Rockstar can't add car deformation due to limitation of the current-gen consoles.