Mackay's men required a point from tonight's home match with Charlton and they got it by playing out a 0-0 draw in the Welsh capital.
"It's been a long time coming but we're here now," Mackay told Sky Sports News after the game.
"It's not really sunk in. There's a lot of smiley, happy faces and it's going to be a long night in Cardiff."
When asked what club he was most looking forward to visiting next year, Mackay named his former club Norwich City.
The Bluebirds are now seven points clear at the top and could wrap up the title on Saturday at Burnley.