The Welsh club have been guaranteed a top-two finish in the Championship after drawing 0-0 with Charlton Athletic on Tuesday night and Mackay says that things are already on the go as they look ahead to life in England's top flight alongside arch rivals Swansea City.
"We're going to plan properly and that's started already and we'll now put that into action," Mackay told BBC Sport.
"We'll make sure the departments we've opened up at the football club and the structure we've implemented keeps striving forward.
"Change is constant and, if you don't go with it, you're left behind.
"We've been changing and adapting, pushing the envelope and trying to get the best practice in every avenue we've gone down. We'll continue that to make sure we give ourselves the best chance we can in the Premier League."