Just worked all this out with sprint tonight. My contract was about to be up, so I had a bit of negotiating power, plus I'm a gold member. I realize that means this is slightly off topic, since I was not in danger of loosing my upgrade.
Sprint (customer service over the phone, sprint stores can't do anything) gave me an extra $100 towards the purchase of both a new phone for me and my wife's phone (she ordered the epic). That is on top of my upgrade. Since the Nexus has not launched yet, she gave me a bill credit in the amount of my upgrade discount + the extra 100. They also changed our nights and weekend minutes to start at 6.
That means I can spend it on whatever phone I want, when I want. I'm going to Best Buy tomorrow to preorder the Nexus. Just thought you all might like to know that this is possible, if you can talk to the right people.