There haven't been a ton of details about the film yet, but it's expected to delve deeper into the mystery of Star-Lord's (Chris Pratt) parentage. In the comics, Star-Lord's father is a fairly obscure character who will probably never appear on the big screen. So don't be surprised if Gunn choose a more prominent character as his daddy. And as for Groot, the assumption is he'll be fully grown after being blown to smithereens and reborn as a tiny dancing sprout.
Guardians of the Galaxy: Vol 2 opens May 5th 2017.