My opinion. If you can get the car at a good price I say go for it. Parts are going to be readly available for quite a while as the 3 has been out for over 3 years and also being one of the most popular cars among racer the demand at the hobby shops will still be high for parts thus being said I would go with the 3.
Also I really don't see the 4 being widely available over the entire country untill spring. If you live down south where they race all threw the summer I would say maybe but for folks up north like me. There really isn't going to be much of a demand for any of the 4 untill spring.
I also think that it is really funny how many people post thoughts from a drawing of not even half of a car. A drawing that really isn't all that great. For all we know they had one of the engineers come up with something real fast one afternoon just for people to do that get all excited and also to get them off there backs.