For a long time the only source of Multis and Stems was remix contests, leaked stems by artists who get them for remixing officially, and of course Harmonix games.

Soon came Jammit with their amazing list of songs all separable within their app (and out of it for some) which was then a big mistake now that Jammit is shut down.

Rockband 4 came out, but those stems aren't really something we can get.
Guitar Hero Live has some good stuff, but they focused on their GHTV part more than getting DLC.

So I ask, when will a new source come out?
Will it be a new game? A new program/app? Even an artist who is finally gone for their copyright to expire and their stems to be publicly accessible and/or requestable (from the Record Labels and Managers)?

Who knows? I hope something like Jammit 2.0 comes out personally. I loved what they did, and really hope no one would mess up their fame that time around.

Tell me what you think might come around, or what you hope might arise.