No, not really. Most, if not ALL smart centers have cars on hand for immediate sale.
I'm only guessing, but I would say that when your lease is up, you should have no problem locating the smart of your choice.
BUT if you want to place a reservation and plop down your $99, then you might want to do it sometime in the next couple months. If you find one on the lot, you can always cancel your reservation and get your $99 back.