Chris Turlach, a Wizards of the Coast staffer, who has been writing about the new Adventurer's League organized play posted a
new article today (presumably, the first of a series) about Factions. There's not a lot of mechanics talked about in the article, but there are some tidbits about how players gain and use "renown." This article emphasizes narrative rewards and the story paths that seem to open up as a character advances within their faction.
Turlach also touches on a mentorship system, where players who reach Rank 2 "can be apprenticed to another higher-ranking adventurer from [their] faction." Rank 4 characters can apparently designate another character of Rank 2 or 3 as their charge. It will be interesting to see how this places out in-game.
The five factions, and a small bit of info on each are written about
here.
