The battery has always been the hurdle in the GPS systems. Any improvement in battery chemistry is still below the horizon.
Where we might hope for some help is the current consumption of the GPS link. The cell phone industry (the 600 pound gorilla in the consumer electronics jungle) is constantly beating on the GPS module makers (nobody makes their own GPS modules), to get the current drain down. We can hope for incremental improvements in the "battery life X update rate" product. For the short term the only way to increase battery life is to decrease the update rate. Marshall has come up with an improvement to their product by adding a switchable higher power mode to the Direct Radio Link (Direct Connect in their terminology). While not the big contributor to the power budget there is a worthwhile savings to be had in keeping the amplitude of the link signal smaller when in VG (Video Game) mode. Bumping the link signal up to get more range in the Medium Range Recovery mode is a consistent addition to Marshall's list of choices in how you use GPS.

Regards,
Thomas of the Details