Mlb released their new Proposals to speed up the game and one of The requests the MLBPA made was to bring back the bullpen cart. Which owners are considering
http://www.espn.com/mlb/story/_/id/22290155/major-league-baseball-proposes-pace-game-changes-no-pitch-clock
More of the proposals can be found hereMLB is ready to accept the union's proposal to study the feasibility of bullpen carts and would introduce the use of carts where feasible in 2018 and 2019.
http://www.espn.com/mlb/story/_/id/22290155/major-league-baseball-proposes-pace-game-changes-no-pitch-clock