Do you want to use Team Foundation Server for non Microsoft technologies such as Java, PHP, Ruby, etc?
Are you concerned about purchasing the licenses for those team members who don't use Visual Studio?
Do you know how much the current development project costs to you? Do you know the utilization ratio of your programmers?
Are you concerned about the long launch time of the new automation system?
Do you think that the functionality of the VSTS/TFS is not sufficient? Do you want any features to be added there?