The overlap between Barry & Wally has been going on for decades now. When Wally first took over as The Flash, he was a much different, and much less sympathetic character. It wasn't until Baron left that Wally became more of what readers love about the character, particularly once Waid took over. However, even then, Wally had begun to assume more of Barry's traits by marrying his reporter girlfriend, facing off against Barry's old Rogues, and getting a job within the Police Department. Once Barry returned, many of Wally's traits started getting absorbed by Barry.
The two characters still have some differences, but their similarities are so pronounced I'm not sure how they'll end up distinguishing the two from each other in their respective roles within the DCU. My preference would be for Wally to become more Multiverse focused, which appears to be where Flash Forward is going.