I think jsk hit the nail on the head about the northwest migration of hipsters in Chicago. After Irving Park & Portage Park, Jefferson Park is likely to become more gentrified as well. Whether or not that gentrification will be preceded by hipsters or not, I'm not sure.
Farther north, Albany Park is likely to become a big hipster area soon, if it isn't already.
On the west side, the area around the United Center could become hipster pretty soon, what with its proximity to UIC, the medical district, and the already gentrified areas just west of the Loop.
On the southwest side, I would say the Clearing area near Midway has some good potential to become a hipster area.
I wouldn't count the suburbs out either. There are a few suburbs that still have that nitty-gritty quality to them and are also relatively affordable (but aren't crime-ridden like Maywood, et al), but remain close enough to the action, especially via mass transit. I think a few places like Villa Park and Berwyn could become hipster areas. Maybe not as hipster as the neighborhoods in Chicago, but hipster enough by suburban standards.