When it comes to movie/tv series content, Netflix is definitely taking the lead here with some of its original production, i.e. Narcos and Marco Polo whose second season apparently is starting this summer. I would expect, as usual, mainstream media would be slow off the mark and behind the curve. Sports is another matter. We saw with the attempt at 3D, the leagues were first to broadcast games in the format and now it seems to be the same with 4K. Live events automatically just look more impressive in the chosen format.
As mentioned on a previous forum, locally, Rogers Communications(Owner of the Toronto Blue Jays)is broadcasting all of the Jays home games this season in 4K and so are the Raptors basketball club going forward. It does make things easier, however, when the owners of both clubs are communication/broadcast companies, and aside from owning the teams, own the sports stations on which they broadcast the games and the facilities in which they play.