As Outer Planets provided more planning sheets, the new expansion (space station, Pluto/TNO, asteroids?) could also provide more components. Given the horrible shipping prices such combos could be welcomed by the fans.
I am really hoping for some locations in the Oort Cloud! TNOs of course as well. Maybe even missions to discover the outer Heliosphere, Termination Shock, Heliopause, Heliosheath, Hydrogen Wall, Bow Shock + interstellar medium. There is still sooo much potential! =)