McNamara was coveted by Blackpool but United rejected the English club's approach for permission to open talks, and the manager says he is so committed to achieving success at Tanndice that he has been looking ahead to next term.
He said: "Nothing has changed. We will just get ready for Sunday and then look forward to next week. There is nothing really more to say about it. I have been working with the chairman for the last few months preparing for next season.
"You have to be ready for different scenarios with players coming in, players out of contract . . . there's speculation about others moving.
"Last year, we lost a few key players like Johnny Russell, Jon Daly, Willo Flood and Barry Douglas so I think we have coped well and have brought good additions in. It will be the same every year."
McNamara wants to win tomorrow's Premiership finale at Celtic but admits their cup showdown with Saints carries more importance.
He said: "To be honest I haven't really decided my team yet. I would imagine St Johnstone would be the same. You want everyone to be fit, fresh and available for next week.
"We have secured fourth spot in the league and there is nothing else that can happen on that side of things. But next week is a lot more important than Sunday for us."
Gary Mackay-Steven admitted he was delighted to hear Jackie McNamara would not be leaving Tannadice, describing it as the ideal pre-Scottish Cup final lift.
He said: "It's a great boost for everyone. He's come in and been a breath of fresh air.
"If anyone is linked with another job it's always a good thing. It shows he's doing something right. He has laid great foundations here. Even in the short spell he's been here, he's brought young players through who're blossoming under him."