A good dozen new cars were added to the League for this season (many of which it looks like you've already unlocked). Additions include a few Hot Ones models and others that were voted on by you.
However, there are more than 50 cars that are still locked and just waiting to be added to your garage. More than 20 of those have a 1200+ rating (some 1300+) so you know they're pretty fast. No reason to save your credits, unlock some cars and try to grab a few extra points towards that grand prize.
Here's the complete list of currently locked cars