Having studied Latin, "collectible" tends to make more sense to me, since "colligere" is a third conjugation verb, and the Latin suffix "-abilis" originally applied only to first conjugation verbs. But looking at the etymology of the word "collect" on Wiktionary, before coming to English it took a detour through Medieval Latin in which the word "collectare" WAS a first conjugation verb. Learn something new every day, I guess.
Apparently American English favors the spelling "Collectible", which might be another reason it's the spelling I'm most comfortable with. It's just one of many American English spellings that makes more sense to me than their British English equivalents after studying Latin and Spanish. I wonder if the similar spellings between American English and these languages is a result of early American trade with Spanish colonies, or a result of American English lexicographers being biased towards Latin spellings.
@BrickByBrick Ninjago always brings out new dragon head moods so that's nothing really new. A new windshield piece used in the back of that tank when they could have just as easily used the old large cone piece doesn't make much sense. I wouldn't be surprised if those designers stuck in there to get us all riled up though.
"Always"? These are the first new dragon head molds in a Ninjago set since 2011. Otherwise, it reused the original three head molds from 2011–2013 and stuck strictly to brick-built dragon heads from 2014 to first half 2017.
A new Falcon could definitely have been a consideration when creating that new mold on the Ice Tank but that's no guarantee that it'd be coming this year, or that it's the only reason they'd introduce a big cone-shaped piece like that.