The Temple Contest was the only one I recall seeing featured on a Devstream, and that was during the Developer Stream - Update 2.6 but it was mainly announced via Forum post
Other contests include:
Valentine’s Day Card Contest Winners which was announced via Forum post
Tower of the Elephant Contest Winners also announced via Forum post.
So, likely the Fashion Contest winners will also be announced via Forum post on the 30th with no ties to 2.9/ 3.0.