Deck Nine has been developing the game for a long time now, yes it's a prequel were you will finally get to explore the relationship between Chloe and Rachael. I think it will be interesting to see Nathan now that the player knows about what he will become but Chloe doesn't. Mostly due to the fact Dontnod is busy on multiple other projects.
My post from yesterdays idol minds thread:
Yep they are working on Life is strange, the story focuses on Chloe and Rachael.