I am feeling some "We are the world" chant coming...
I think it will happen to where it is standardized. I envision nav/gps systems being standard. So much so that it is as much an additional feature as seatbelts are. Hardware wise they will probably all use ARM/snapdragon/x86 processors which linux can run off of. People like us will move into software modding mostly and get it exactly as we want, some will take notice and eventually there will be a firmware update that will replace whatever OEM software with some hacked linux version that works much better.
Sort of like how people that dont realize the optical drive isnt a cupholder can burn a DVD, put it in there Lexus/Toyota and change the nav software with a key combo.
Mainstream I dont think it is going to happen, and I think above is the best we are going to see for a long time.