It depends entirely on the new model year build date at the RV manufacturer. I ordered a 2015 Siesta on April 10th 2015- I was informed by the THOR factory later that month they were no longer accepting orders for the 2015 model, mine would be the first of the 2016 model year. My delivery date was June 15th of 2015, a 2016 model.
More complete explanation of split model years here:
http://www.winnebagoind.com/resource...Motorhomes.pdf
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