It'll never be a real competitor, Google Maps is available on a range of platforms. Apple maps is available exclusively on iOS. Apple maps has no novel and useful features that Google Maps doesn't have, Google Maps has novel and useful features that Apple Maps doesn't have.
As it sits, Google maps is the Coke or Pepsi and Apple maps is the store-brand soda. You know, the stuff you get if you're too cheap to buy the good stuff. I can't see that changing at any point in the future.