The Pole is expected to lead his nation’s front-line against Greece in the Euro 2012 opener, and was an integral part of Jürgen Klopp’s Bundesliga-winning side last season, bagging 22 goals along the way.
It is that sort of form that has attracted some of Europe’s top clubs but, according to Smuda, Lewandowski’s destination has already been confirmed.
"In my opinion, in a moment they will be gone from Borussia," Smuda said.
"Lewy' [Lewandowski] is going to Manchester United, Kuba [Blaszczykowski] also somewhere in England, [Lukasz] Piszczek to Real Madrid.
"They have a goal and they want to grow. I base the squad on them."
The 23-year-old centre-forward is yet to agree an extension to his current deal with Dortmund which expires in 2014, fuelling speculation that he could be moving elsewhere.
United manager Sir Alex Ferguson was spotted in the stands at the German Cup final as Dortmund beat Bayern Munich 5-2, a game in which Lewandowski scored a hat-trick.
However, after the departure of exciting Japanese prospect Shinji Kagawa to Manchester United this week, Die Schwarzgelben are adamant no more key players will be leaving.
Having agreed a contract extension with centre-back Mat Hummels, managing director Hans-Joachim Watzke Watzke said: "We expect Kagawa to go, but no amount of money will persuade us to sell the others."
With Dimitar Berbatov widely expected to leave Old Trafford this summer, Ferguson is looking to strengthen his attacking options, with Chilean youngster Angelo Henriquez also thought to be on the club’s radar.
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