Curated brand mashups offering a collection of consumer targeted lifestyle products to enhance and elevate the parent, or curator's, image by leveraging another brand's expertise, history, etc. (e.g. JCrew/Belstaff).
Not in the "designer name here for Target" way. We've been there done that.
As far as trends for youth, I think we will continue to see simpler, more modest clothing for both guys and gals. The adolescent need to physically display social identity via clothing choices is quickly losing its importance against highly customizable social network profiles.
This change is certainly being felt by niche and fringe retailers that used to be the places for edgy scene wear.
Unique clothing will always be a part of the experience of youth, but I think we are seeing a significant change as a consumer priority.
I would say it's a similar trend to what we'll see elsewhere in advertising - brands will be creating original content in order to drive their narratives.