Depends on what he means by "end of summer", but depending on his allocation, that sounds like a fair estimate. As you've probably seen from other posts, there's no hard and fast rule to how these things go. What -will- work in your favor is the backlog of cars starting to be cleared out, the factory ramp-up in production numbers, and the addition of those Saturday shifts
You might do some digging/asking about how many he's already had delivered, how long it took for them to be picked up, and how their Corvette sales have been.