The current Apple Watch doesn't have GPS and it still only lasts for one day. Adding GPS to a smartwatch focused on complementing your smartphone and providing mobile apps just doesn't make sense.
Rumors of a new Apple Watch continue to appear with the latest from a KGI analyst stating that one model, the Apple Watch 2, will include GPS, a barometer, and water resistance. GPS and constant hear rate monitoring requires lots of power and unless Apple significantly increases the size of the battery or announces some new battery technology, adding GPS should not be a priority for the Apple Watch.
The Apple Watch is an excellent smartwatch, but it's not a GPS sport watch and should not attempt to be all things. In my experiences, many people with an iPhone run with their iPhone in hand or mounted on their body so compromising the Apple Watch to include GPS is likely targeting a very niche market.
Those people serious about tracking their running or other outside activities are also likely to have a dedicated GPS sport watch that doesn't compromise their training experience. Given Apple's rather open nature with Apple Health you can use a number of GPS sport watches and have that data synced to your iPhone.
When I purchased and wrote my review of the Apple Watch I lamented on its lack of GPS too. However, we've seen Android Wear devices, such as the new Polar M600, appear with an integrated GPS receiver and the battery life is seriously compromised by including GPS in a device focused on the smartwatch experience. Polar's current GPS sport watches last a long time, but battery life is now down to just two days when you add in a mobile operating system and full smart watch capability.
We've gone through times of consolidation throughout the history of mobile devices, but the end user experience is usually better with focused devices. Athletes get a much better experience with dedicated GPS sport watches and given that the public still has not widely adopted smartwatches, Apple and Google should focus on making a compelling smartwatch experience while leaving the fitness tracking up to companies like Garmin, Polar, and Fitbit.