Winter '16 release notes - Automatically Get Geocode Information for Addresses
In Spring '16, we plan to add geocode information to all your accounts, contacts, and leads.
I don't think there is currently any native geocoding currently available with that control.
By all accounts, the apex:map control is using a third party service via JavaScript to create the map and perform address to lat/long geocoding.
It would be a hack, but you could try and interact with the resulting JavaScript and DOM to extract the lat/log results. It would probably be fragile. Maybe do the geocoding directly with a third party service?
There is the idea Spring 15 Maps Feature should populate lat and lon on the address fields., which includes details about the Salesforce Summer '15 Geocoding Pilot.
Got geocodes? In the Salesforce Summer '15 release, we are piloting a new geocoding capability where we add geocode information to your standard addresses in Salesforce.
Geocode information, which includes latitude and longitude for addresses, can be used to assign territories, segment markets, target specific areas, and analyze demographics. The pilot will focus on the first step - populating the latitude, longitude, and accuracy fields for standard addresses in accounts, contacts, and/or leads.
Follow this link to learn more! http://goo.gl/forms/qNRLdcTphw