CONFIRMED: I cancelled my old reservation and the Plus models available showed up as in stock. I had to change the store and time for my reservation, but I was able to get the model I initially wanted for a Friday pick up.
Thanks to MacRumors forums, yet again!
I did this as well. I had a Gold 7+ 128GB reserved. I canceled my reservation and was able to reserve a Black 7+ 128GB. Kind of nerve-racking canceling my reservation...but I'm glad it worked out!