The Bluebirds secured promotion from the Championship by drawing 0-0 with Charlton on Wednesday and could be confirmed as division winners by Saturday, though the boss is already considering the next challenge, with talk of £25 million to spend.
"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.
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"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."
Mackay has been keen to divert praise from himself for this season's success onto owner Vincent Tan, who invested into the club after controversially changing the team's colours from blue to red.
"This season is probably when he's gone hands-on at the club," said the Cardiff boss of Tan's influence. "In that respect there's been a lot of firsts for him in terms of learning about the game, the football club, the division and life in south Wales.
"A lot of credit has to go to him for adapting to that because he's a very successful businessman in his own part of the world. He's got his finger on the pulse over there.
"For him to come over here and give trust in me and my staff and allow me the chance to bring a group of players together I felt that could be promoted is great."