At the time Destiny was shown off in the second opening, had its design already been revealed in Newtype magazine or promotional shit? Or was this how it was first teased?
Since by the time we actually see Destiny Gundam it's already OP3

I think it was revealed in a magazine a short while after this but the shadowed version in OP 2 was the first time it was shown. Freedom was shown similarly in SEED's OP2

>>23310672 (OP)
When they showed the OP, it was brand new and no one had seen it before. I remember discussing it with fans on forums wondering what the design would be. Then like a week or two later they released full images of Destiny Gundam in magazines.

>>23310672 (OP)
No, it seems they kept the design under wraps and did not reveal the full design until it appeared on screen. Destiny's second OP started airing by episode 14 which was January 15th 2005, but the AEUG blogspot archives indicate that magazine art featuring the Destiny's design wasn't leaked until March 7th 2005.

https://aeug.blogspot.com/2005/03/#111021061219356530
>Early copies of this month's anime mags have leaked out. Pics of the Destiny Gundam have already been posted on imgboards and such

The Destiny's design was apparently revealed on March 5th 2005. I have no idea when the gunpla commercial started airing, but it's a good bet it would have been the same day as the new episode since TV contracts tend to work like that.

https://aeug.blogspot.com/2005/03/#111001503036210381
>And the commercial revealing the new design also formally announced the 1/144 Destiny Gundam kit for "this Summer"

The weird thing is I swear Generation of C.E. was the first time Destiny and Strike Freedom were actually shown outside the OPs and that's how we first found out about SF's Dragoons and Destiny's "Shining Finger" but according to the release dates that wasn't the case.