It seems pretty clear that Hummel will make the roster which leaves the last roster spot to either point guard A.J. Price or big man Chris Johnson. Although Johnson has the guaranteed money, I don't see how they could keep him. There's no playing time behind all the other big men on the roster, he saw less than 10 minutes all of preseason and the Wolves need another guard in their backcourt.
Assuming that Hummel & Price make the final roster, the depth chart would look like this...
PG: Ricky Rubio, J.J. Barea, A.J. Price
SG: Kevin Martin, Alexey Shved
SF: Corey Brewer, Robbie Hummel, Shabazz Muhammad, Chase Budinger
PF: Kevin Love, Derrick Williams, Dante Cunningham
C: Nikola Peković, Ronny Turiaf, Gorgui Dieng
Both Jeffers and Brown could play for the Wolves' D-League affiliate (the Iowa Energy). I know Jeffers is a free agent, however I don't know if Brown could technically sign with another team or if the Wolves still own his rights. I would assume since they waived him he's a free agent, but I honestly have no idea.
The Wolves' roster currently stands at 16 and the final 15-man maximum regular season roster is due by Monday (Oct. 28) by 4pmCT. Will have more on this before then, stay tuned!