Going forward, there's plans for GNOME Maps to work on route search support using GraphHopper, support for locating nearby points of interest, contact data integration within Maps, Facebook and Foursquare integration support, improvements to Map markers, and support for GNOME Maps to communicate with other apps like GNOME Weather and GNOME Clocks.
Going further out are plans to add/update the OpenStreetMap database via GNOME Maps and to create custom overlays.
It will be interesting to see how GNOME Maps does given that Google Maps provides these features already and it does so extremely well, along with plenty of other maps applications out there. GNOME also doesn't have a big install foot-print on mobile devices right now so it will be of limited reach to many for actually using the application while traveling.
More details on the GNOME Maps plans can be found via this blog post by Jonas Danielsson, one of the GNOME Maps co-maintainers.