Thank you to everyone who helped us think this through!
Thanks to a fellow forum member we found a 2016 that was already on order at a dealer in Michigan which would have been ready mid-July and given us some more cushion on time. We had been leaning that way, but then...
The more-local dealer we had been working with on ordering one to our spec was able to find a 2015 Elite sitting at a friendly dealership somewhere in Indiana and convince the dealer to let him sell it. Cost us a bit more in increased freight, but still came out under 70% of MSRP.
If all goes well it'll be picked up from the other dealer later this week, and then we'll be able to pick it up shortly thereafter.
We did give up the new 2016 features, but decided the certainty of having one in time as well as giving the more local dealer our business (and therefore having a better advocate for service, etc) was worth that trade off.
For the record - our next trailer (assuming there is a next one) will be purchased in the fall and not in a hurry so we can take advantage of even better fall/winter pricing and avoid this stress!
Thankfully, though, this all worked out! Time to start planning our trip!!!