"Many developers left the company, no map improvements planned for iOS 8 release were finished in time. Mostly it was failure of project managers and engineering project managers, tasks were very badly planned, developers had to switch multiple times from project to project"
While another source said "I would say that planning, project management and internal politics issues were a much more significant contributor to the failure to complete projects than developers leaving the group."
There is still a chance to see Maps App get updated in the upcoming IOS 8 Betas or even in IOS 8.1. We are gonna have to wait and see if that ever happens.