GT Sport will have a new update today, it is in fact availableUpdate 1.38. Here is the Press release by Playstation:

A new update for the April update of GT Sport is available for all the passionate riders who can now compete with the classic European racing cars and the elegant all-wheel drive roadsters that have made motorsport history.
At this link you can find the video of official presentation of the new patch 1.38.
Additional information is available on PlayStation Blog.
Gt Sport cars available
Compétition de France