For a customer I’m preparing a roll-out of Team Foundation Server 2015 once it is released(yes, I know it’s still in CTP). The server guys were asking for the hardware and software specs, but I couldn’t find a definitive list of system requirements.
The only somewhat useful/official information I could find was in the comments of a blog post by Brian Harry.
If Brian is right(as the TFS Product Unit Manager, he should be), requirements will probably stay the same as for TFS 2013.