Looking for some guidance please.

I am 75K. Have the Citi Prestige card thus the $250 credit and have already used my 2015 credit. My companion cert expires on 12/21 this year.

I want to book 2 tickets to Hawaii but in 2016 so I can use that years credit on Citi and the companion fare. Will the trick still work to book something this year, then change to a higher fare for next year and use the $250 cert? Doesn't seem like I'd net any savings that way and the companion fare is basically irrelevant.

Thoughts or tips?