After listening to episode 321 of The Azure Podcast[0] my understanding was that Azure DevOps would eventually be phased out; question begins at ~10:30 and at about ~12:00 a rough timeline of 5 years was given with guidance to select GitHub if just starting out.
0: http://azpodcast.azurewebsites.net/post/Episode-321-GitHub
The writing is on the wall... TFS is going the way of Silverlight.
Very valuable comment / insight via the podcast – thanks!