Nokia has said in an interview with TheNextWeb that they are winding down their development of HERE Maps for Windows Phone in favor of releasing on iOS and Android. HERE Maps has been filling the void of Google Maps on Windows Phone since the beginning. Now the Windows Phone app won't receive the same kind of attention it has in the past. Nokia has no plans to stop developing for Windows Phone, but they are taking resources from Windows Phone development and moving them to other platforms.
After Microsoft acquired Nokia's devices and manufacturing division, Nokia's mapping division has become unshackled from the strong tie to Windows Phone. This will open the door for HERE Maps to invest in iOS and Android. Nokia did bring HERE Maps to iOS 7 for a short period but had to remove the app due to internal issues with the app. Now Nokia plans to rewrite the app from the ground up to work on iOS.
Nokia has already announced a partnership with Samsung to bring HERE Maps to Galaxy devices including their smart watch. This app will be a Samsung exclusive to begin but will eventually hit all Android devices. This is good for Samsung to have compelling alternatives to the Google services and gives them more leverage with Google. HERE Maps will come into direct competition with Google Maps on iOS and Android unlike Windows Phone which has no Google services.
To compete, Nokia believes they have an advantage with offline maps. Allowing users to download regions of the world for offline navigation is very helpful and unique. This feature is on Windows Phone and has proved very useful. The new small Nokia has not shared their plans for monetizing HERE Maps on these other platforms yet. The mapping data owned by Nokia is licensed to range of other companies including car companies for navigation. These apps could be a tool for Nokia to gather data on driving patterns to improve their maps or they could eventually serve ads: it is still unknown.
UPDATE: To be clear Nokia has made a statement saying they remaining on Windows Phone. Making HERE Maps for iOS and Android will increase the users of HERE Maps and increase the data and feedback which will be used to improve their services across the board. If you are a Windows Phone user and you love HERE Maps don't fear, your maps aren't going anywhere.