No, you will only get the Diamond choice benefits selection once. You'll be able to select them from when you first qualify in 2016 through the end of the 2017 program year, but you only get it once (unless you re-qualify for Diamond in 2017 which will add another set).
Ok, so just so I make sure I've got this... If I hit DM for 2016 in 2015, I get to chose 2016 choice benefits.
If I hit DM in 2016, I also get to chose 2016 choice benefits, but the status will last through 2017? (And I only get to select 2017 choice benefits if I requalify for DM during 2016?)